-ON THE WEST INDIAN SEAL (MONACHUS TROPICALIS, GRAY).

VI

-ON THE WEST INDIAN SEAL (MONACHUS TROPICALIS, GRAY).

BvFredkrick W. Truk and F, A. LucAS.

lu October, 1883, theXatioual Mii«ouiii received, through thekiudly offices of ^Prof. Felipe Poey, of

Havana,

Cuba, the

mounted

skin of a seal which

had

been on exhibition in that city during the

summer

of the

same

year.

The

seal

was

reported to liave been captured in the vicinity of

Havana. Upon

arrival at the

Museum

^it provedto be, as ]*()ey

had

suspected, asi)ecimen of the seal which

Gray had

i)rovision- iilly referred to the genus 21onachus, under the

name

of

M.

tropicalis.

The

skin

was

imperfectly prepared,

and

it

was deemed

advisable, there- fore, thatitshould beremounted.

Upon

examinationit

was

found that

tlie skull

was mounted

inthe skin,

and

that the bones of the fore

and

hind flippers

had

not been removed.

Owing

to this Ibrtunateaccident

it is possible todescribefor the firsttime thecranial characters of the

si)ecies.

The

specimen isafemale,

and

apparentlyadult,thoughnotaged. Its length, measured from theend of thetail to the extremity of the muz-

zle, ina straightline, isfifty-three inches.

So

far as external characters are concerned, the

Havana

specimen agrees with thedescriptionof Gosse, published in his

"A

Naturalist's Sojourn in Jamaica," which appeared in 1851, and with that of Gray, founded upon animperfect specimen

now

oruntil roi^ently inthe British iVIusenm. It presents, however, several minorditi'erences,the

more

im- portant ofwhich

we

will

now

proceed to discuss.

The

discrepancy which firstmeets ourattention relates tothecolorof the whiskers. Theseare stated by Gosse to be of a "black hue, with transversebars of gray." In the specimenbefore us the whiskers are horn-colored, with blackish tips.

The

colorof the body is described by Gosse in his earlier pages as

"intenseanduniform black"; but subsequently,

when

treating ofaspeci-

men

capturedbyWilkie, hegivesadifferentdescription,and one which, with very slight modification, is ai)pli(;al)le to the 8i)ecinien before us.

The

fur of Wilkie's specimen is said to have been ^"nearly uniCorni dirty ash-gray; black at thebase

and

gray at the tipsof the hairs. It

331

332 REPORT OF NATIONAL MUSEUM,

1S84.

isslightly mottled ou thebelly." Inoar specimenthehairs oftheback

and

hind flippers appear light at the tip, as ^if faded by age; but are dark sei)iacolor or nearly black, excei)t at the extremity.

On

the under parts

and

on thesidesof the body, neck,

and

head the darkhairs are interspersed

by

others which are white except atthe tip.

The

lips arebordered with white.

On

the upperlips the hair above the white fringe isdarker than that of thesurrounding surfaces.

The

palmsare notbare,as stated

by

Gosse, butareequallyas wellclothedasthe upper surfaces of the flippers. It isprobable that the specimendescribedby Hill had worn thehair from the iinder surfaces of the flippers by con- tact with the dry surfaces of theinclosure in which it

was

^confined.

The

skull.

— The

skullbeforeus presentsnocharacters which would warranta separation of the species generically from

M.

albiventer, the typeof thegenus Monachus.

The

specimen agrees perfectly with the diagnosis of the genus given

by Gray

in the Hand-list of Seals, &c.

(1874, p. 11).

In general form the skull is depressed

and

elongated, the breadth being exactly three-fifths the length.

Compared

with Plioca vituUjia, the muzzle is

much

less tapering; viewed fromabove,its sides are ap- proximatelyparallel.

The

intermaxillaries meet the nasals and extend alongtheir sides for abouthalfaninch. Nasalsnarrow,

somewhat

less

than one-fourth the length of the skull, and emarginate anteriorly.

The

interorbital regionisbroad, withparallel sides,

much

as in Erig- nathns.

The

frontals arein contactwith thetemporalsposteriorly, and

to a greater extenton theleftthan on the right side.

The

contour of theparietals is rudely square, the posterior margin beingemarginate.

In the specimen under consideration the sagittal

and

occipitoparietal sutures arestillopen.

The

sagittal

and

lambdoidalcrestsarerudiment- ary.

The

malar rests

upon

the maxillaryanteriorly.

A

^line

drawn

from the outer edgeof the canine parallel to the median line cuts thean- terior endof the malar.

The

maxillary supports the malar internally for

more

than half the length of the latter.

The

articulation of the malarwith thesquamosal presents no peculiarities.

The

^"palate" is strongly contracted at the juncture of the anterior

and

middle thirds,andacutely emarginatebehind.

The

posterior pala- tine foraminalie wholly inthemaxillary.

The

^posteriornaresis small; itsmargin forms anequilateral triangle.

The

narial

septum

is veryincomplete.

The

auditory bullae are pyriform inoutline

and

depressed, the upper surface traversed

by

a distinct groove.

The

lateral extension of the bullaformingthe wall of the meatus anditoriusis incompletein front.

The

anteriormarginofthebulla isdeeply concave.

The

bulloediverge strongly posteriorly.

The

foramen

magnum

is broader than high.

The

paroccipitals are well developed,short,

and

thick.

WEST

INDIAN SEAL.

333

The

mandiblepresents

some

remarkable peculiarities.

The

condyle

is verylow, beingon alevel with the alveolarborder of theJaw.

The

coronoid processis welldeveloped and is strongly reflected.

The

lower border of thehorizontal

ramus

isstraight.

The

lengthofthesymphysis

is contained three and a half times in that of the

jaw

; the symphysis

itself isvery thick.

The

fnriow below the condyle, in which the ex- ternal pterygoid muscle is inserted,

and

which is so strongly

marked

in mostseals, is scarcely apparent inthe specimenunderconsideration.

Dental formula as follows: J.|; C. _i; M. _f

x2 =

32.

The

line of

Iheupi)er incisorsis straight.

The

outerincisorsare

much

largerthan the inner ones.

Both

pairs are uuicuspidate.

The

inner pair has a slightly

marked

cingulum internall.^, while the cingulum is strongly developed in theouter i)air

The

superiorcanines are short,stout,and rugose,

and

bear arounded ridge posteriorly.

The

second

and

third molars are set veryobliquely, the anterior end being turned inward.

The

first and fourth molars are less oblique, the fifth not at all.

The

second, third, and fourth molars are ai)])roximately equal in size, the

first

somewhat and

thefifthdecidedlysmaller. All the molars are very rugose, and,except the fifth,are furnished with anobtusecentralcusp, supported before

and

behind by a smaller accessorycus]).

The

fifth

molarhas noaccessory cusps.

The

cingulum is strongly developed in all the molars, and, except in the first, ends anteriorly and posteriorly in a small denticle. Only the i)osterior denticleis present in the first

molar. Except between the first

and

second molars interspaces are wanting.

The

first molar rests against

and

is half internal to the canine.

The

molarsare two-rooted,except the first.

The

lowerincisorsaresmallerandmore obtusethantheupperincisors:

the innerpairsmallerthan theouter, internal to the latter,and decum- bent.

The

short canines have a i)Osterior

and

two internal vertical ridges.

The

description of the superior molars appliesequally to the interior series,except that thefifth islargerthan thefirst

and somewhat

oblique,

and

that there ^is no interspace between the first

and

second.

The

line of theinferior molars is straighter than that of the superior molars.

Comparisonof

M.

trojpicalisand

M.

albiventer.

Ifthe specimen before us is adult (and the condition of the skull would seem to indicate that it is),the

West

Indiansealmustl)e consid- erably smallerthan M. albiventer.

The

femaleofthe latterspecies de- scribedbyF.Cuvier(Ann.

M^m.

d'Hist.Nat.,xx, 1813, p. 387)measured

7to8feet* from theextremity of the muzzle to theend ofthe hind flip-

l)er. In the

Havana

specimen the total length is but 4 feet and 10

inches.

The

male

monk

seal described by

Hermann

in 1770 differed widely from the animal beforeus, in that theunder parts were verylight

and

•French measure.

334 REPORT OF NATIONAL MUSEUM,

1884.

thatthere

was

alarge square area ofsoiled white ou the

abdomen

aud

numerous

grayspots ou the head.

The

coloratiouof the female

mouk

sealdescribed

by

Cuvier{I. c.) approximates

more

closely tothe speci-

men

beforeus.

The

undersurfaces oftheformer were yellowish light gray, while our specimeu is of a yellowish

umber-brown

color in the

same

region.

Much more

important differences arefoundintheskull. In theOsse- mensfossiles^(vol.viii,1836,p.442-443),Cuvier givesatableofmeasure- mentsof the

head and

other parts of the skeleton of a specimeu of^j¥".

albiventer.

Although

Cuvier's specimen

was

larger than that under consideration, the differences aresuch as, in ouropinion, could not be entirely

due

todisparitj' ofage or differenceofsex.

The

width of the zygomaticarch in the former is

much

the greater, beingaboutthree- fourthsthe length of theskull; in M. tropicalis itswidth isonlj' three- fifths the

same

length. This character is

shown

also in the close ap- proximation of the coronoid processes and condjies in

M.

tropicalis.

While

the length of the muzzle

compared

with thatof the brain-case is practically equal in the

two

species,its widtn is considerablj^ less in

M.

tropicalis than in

M.

albiventer. Both the measurements

aud

figuresof the latterspecies

show

that it has the forehead

much more

elevated,

and

consequently the anterior nasal opening

more

nearly vertical, than is the case in 31. tropicalis.

The

foramen

magnum would

appear to be twice as large relativelyin

M.

tropicalis asin Jf.

albiventer. This characteris perhaps of little value,ou account of the great variability observable

among

different individuals.

A

characterwhichisapparently of greatimportance isthe difference intherelativelength of themolar series. In

M.

tropicalisthe length ofthemolarseriesofeach

jaw

isvery nearlyone-third that of theskull, whilein the Mediterranean sealitisless than afourth.

The

condyle of the mandiblein

M.

tropicalisis noticeably low,being on alevel with thealveolarborder of the jaw.

Ou

account ofthis disposition of parts theloweredge of the occipital condyles is in the

same

plane with the lower marginof the mandible

when

the

mouth

is closed. There ap- pearstobe no approachto this arrangement of parts in

any

other ear- less seal.

It isstatedboth

by

F. Cuvier

aud by

Keyserling

aud

Blasius (Fauna Deutschland, 1857, p. 245) that in

M.

albiventer the first upper molar

is thesmallest ofthe series. In 71/.tropicalis this tooth is considerably largerthan the fifth.

Cuvier has figured the skullofii. albiventerwith a prominent supra- orbitaltubercle,a processwhichisentirelyrudimentaryinourspecimen of

M.

tropicalis.

In our opinion the differences pointed out are quite suflQcieut to warrant the separation specifically of the subtropical seals of the Eastern

and

"^Vestern Atlantic. It is decidedl}^ probable that fresh specimensof equal size

and

age from the

two

regions

would show

dif-

^^^:ST Indian seal.

335

fereuces of external proportionswhich cannot be determined from the scanty material

now

atour

command.

Specific diagnosis.

MoNACHUS

TKOPiCAJLis, Gray.

I'huva trvpimlis.Gray, Cat.Mam. ^{Brit.Mas., pt.ii,} Seals, 1850, p. 26.

Phoca Wilkianus, Gobse,Naturalist'sSojourninJamaica,1857,p.308, foot-note.

MonacliHiIropicaUs, Gray, Cat. SealsandWhalesBrit. Mua., 1866,p. 20.

"Monachusf tropicalia, Gray,"Allen,Monogr. N. A. Pinnipeds,1880, p. 708.

Color above umber-brown.

Below

slightly lighter

and

tingedwith yellow. Flippers of thecolorof the back. Lips bordered with white.

Solesandi)alms clothed with shorthair.

Skull.

—

^{Forehead depressed. Condyles of} mandible on alevel with the alveolar border of the jaw.

Length

of themolar series one-third that of the skull. Lastupper molar smallest.

Meusurementa of ^theskullsof Monachus uliiventer {from Cuvier, Oas.Foss.,viii, 1836, 442)andMonachustropicalia.

Measurements.

M. tropicalia.

lOOths.

M.albiventer.

lOOths.

Summitofoccipitalcresttoanteriorbordersof premaxillaries...

Ditto to anteriorextremityofnasals Greatest breadth betweenzyRomatic arches Lea.stbreadthof interorbital ridge Breadth of muzzle on alinewith theincisors

Height from lower borderof occipitalcondylesto summitof occipital crest

Fromthealveolarborder of the maxillaryto the anterior ex- tremityoftliofrontals

Heiphtof foraiueumagnum Widthofforamenniaguum Lengthofsuperiormolarseries

Distancebetween outer bordersoflastmolarB Dittooffirstmolars

Totallength oflowerjaw

Angleofmandibletouppersurfaceofcondyle ^, Angleofmandibletoextremityofcoronoid process

Distancebetween outer borders of coronoidprocesses Distancebetweenexternalextremities ofcondyles ,

Lengthofthesymphysis mandibuli ,

Lengthofthelowermolarseries

Bistancebetween outersurface ofcanines ,

193 152 122 25 45 70 45 27 33 60 63 35 134 27 45 89 112 37 60 27

100.0 78.9 63.1 13.1 23.6 36.8 23.6 14.4 17.0 31.5 32.8 18.4 69.7 14.4 26.3 46.0 57.8 19.7 31.5 14.4

282 219 215 32 78 96 01 23 27 65 84 48 210 63 102 161 190 58 54 51

100.0 77.7 76.2 11.3 27.7 34.0 32.3 8.2 9.6 23.1 29.8 17.0 74.5 22.3 30.3 57.1 67.4 20.6 19.2 18.0

Report Nat. Mus.lti^4.-Trueand Lucas. West^IndianSt-al.

PLATE

I.

=5 f^

t t

O

a

EeportXat.Mus.1884.

—

Trueaud Lucas. "WestluJiaii Seal.

PLATE

II.

Skull of MonachiistropicaJis, Gray. Viewfromabove. Two-tbirdsuaturalsize.

(Drawn byF.A. Lucas.)

KeportXat.Mus.1884.—Trueand Lucas. WestIndianSeal.

PLATE

III.

?kullof Monachusiropicalis, Gray. Viewfrombelow. Two-thirdsnaturalbize.

a. Teetli,seenfrominfront.

(DrawnbyF.A. Lucas.)