NO. 2 GASTROPODA — KNIGHT 87 mens cannot be identified with any of these three species but in some

respects are closer to that

from

the

Word

limestone of the Glass mountains.

Figured

specimen.

— ^{U.S.N.M. No.}

^116632a,

Horizon and

locality.

—

Highest Permian, loc. 8o6t.

PLEUROTOMARIA(?),

species

A

Plate 24E, figure 24

Pleurotomaria {?), species

A,

is represented in the

Mexican

col- lections

by

three poor specimens, all

from

a single locality.

They

are merely fillings, orcasts, of the interior of the shell. Nevertheless the speciesappearstobelongtoan undescribed pleurotomarian genusthat yields casts that permit generic recognition with reasonable certainty, at least within the range of its stratigraphic occurrence.

Two

un- described species of this genus occur in the

Permian

of west Texas.

One

isseeminglyconfinedtorocks ofLeonardian ageinboththe Sierra Diablo

and

Glass

Mountains and

the other is

known

only

from Word

limestone

No.

ⁱ in the GlassMountains.

Figured

specimen.

— ^{U.S.N.M. No.}

^116627a.

Horizon and

locality.

—

Leiorhynchoidea-Cancrinellazone, loc, 8o6i.

PLEUROTOMARIA(?),

species

B

Plate 24E, figure 25

Pleurotomaria {?), species B, is represented

by

a single specimen, a coarsely silicified

and

badly weathered shell

showing

the

form and

thegeneralnature of theornamentation.

The

shell

shows

a turbinate

form

withtheareaabovethe selenizonewellarched.

The

outer

whorl

face

below

the selenizone,

which

^liesataboutthemiddle of the whorl,

shows

a nearly vertical lateral area just beneath the selenizone, sepa- rated

from

thegentlyarched base

by an

obtuseangulation.

The

seleni- zone is relatively broad

and shows

as a gently concave

band between

two

borderinglirae.

On

thewhorlsof thespireitfallsa short distance abovethe lower suture.

The

ornamentation appearsto consist of fine revolving lirae, so far asitis preserved. All these features

show

that the species belongs to

an

undescribed genusthatis represented inthe

Permian

rocks of west

Texas by

six undescribed species ranging throughout the rocks of Leonardian age

and

into

Word

limestone

No,

^I, In spiteof its poor preservation I

am

inclinedto identify the

Mexican

specimen as belongingto aspecies occurring in

Word

lime- stone

No.

I intheGlass

Mountains

ofTexas,

88 SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. II9

Figured

Specimen.

— ^{U.S.N.M. No.}

^116628.

Horizon and

locality.

—

Leiorhynchoidea-Cancrinellazone,loc. 8o6i.

PLEUROTOMARIA(?),

species C

The

single specimen to

which

the above tentative designation is

given, while very poorly ^preserved, suggests characteristics that are

worthy

of

mention

even

though

one cannot be certain of them.

The form

appears to be rather low

and

flat, almost rotaliform.

The

upper whorl surface slopes

outward and

gently

downward from

the

upper

suturewith verygentle convexity.

The

outer

whorl

face, sepa- rated

from

the upper

by an

obtuse angulation, slopes steeply

down- ward and

little, if any,outward. It is separated

from

the very^gently arched base

by

a second obtuse angulation.

What

appears to be the selenizone lies atabout the middle of the outer

whorl

face. Itis nar- row, concave,

and

bordered above

and

below

by low

lirae.

The um-

bilicalregion

seems

to be surrounded

by

a^callus.

The

ornamentation consists of revolvinglirae,seemingly finer

and more numerous on

the basethan onthe uppersurface.

Ornamentation

otherthanthe seleni- zone appears tobe lacking

on

the outer whorl face. Itis possible that this is a

mashed

specimen of Pleurotomaria {?), species B, but ^this does not appear to be true. In

any

case I cannot recognize in the specimen

any

species or genus with

which

I

am

familiar.

That

it is

a pleurotomarian in the broadest sense,

seems

to be very probable.

Described specimen.

— ^U.S.N.M. No.

¹16634.

Horizon and

locality.

—

Spiriferellina zone, loc. 8o6d.

OMPHALOTROCHUS(?),

species

A

Plate24F, figures26,27

The

singlespecimenrepresentingthis speciesisthelargest,the

most

striking,

and

the best preserved in the collection. It has the

form

of a flat, based cone with a pleural angle of 55°.

The apex

is badly abraded

and

largely missing,

and

although

enough

of the baseis pre- served to

show

that it is quite flat

and

narrowly

phaneromphalous

it,

too, isin

bad

condition.

The

specimen is about 25

mm.

^{high, itsbase}

has a diameterofabout 27

mm., on

itsumbilicusa diameterofabout₃

mm. The

sidesof thewhorlsslopeflatly

outward and downward from

theupper suture inconformity withthe conical shape ofthe shell for aboutthree-fifths the whorl height.

The

lower two-fifths is occupied

by

a raised area, gently concave

between two

costae, that

might

be mistaken fora selenizone.

The

upper of the

two

costae is the

weaker

NO. 2

GASTROPODA — KNIGHT ₈₉ and

the

more

restrained of the two.

The

lowercosta projects

outward more

strongly

on

thewhorlsof thespire

and on

thefinal

whorl forms

a flange

around

the base. This raisedarea, withits bordering costae,

forms

a conspicuous spiralribbon

winding

abouttheconeof the shell.

Unliketheother specimensof the presentcollection, thisone

shows

a

few growth

lines.

These

are preserved

on

theflat

upper

three-fifths of the outer

whorl

face and, very obscurely, across the raised area.

Beginning at the upper suture they curve gently

backward and

then

forward

indicating a gentle

and

broad sinus in the outer lip at this position.

Below on

the raised

band

they pass

more

strongly

forward

indicating that the lower costa or flange projected rather strongly

forward

atthe base of the aperture.

They

cannot be followed

on

the base.

There

is

no

ornamentationotherthanthe featuresmentioned.

This species is referable to an undescribed genus of several unde- scribed species widely distributed in Leonardian

and

lower

Guada-

lupian rocks of west Texas.

Perhaps

because they have not yet been studiedsufficiently, I

am

unabletoidentify the

Mexican

specimen with

any

of thewest

Texas

species although thereis

no

doubtwhatever as tothegeneric consanguinity.

The

relationsof this as yetundescribed genusto

Omphalotrochus

(s.s.) willbediscussed elsewhere.

Figured

specimen.

— ^U.S.N.M. No.

116625.

Horizon and

locality.

—

Leiorhynchoidea-Cancrinellazone, loc, 8o6i.

STRAPAROLLUS(?),

species

A

Plate 24G,figures28-32

This Species is represented in the

Mexican

collection

by two

very roughly silicified specimensthat

show

little

more

thanthe shape.

The form

is thatof a

low dome. The

whorls are gently flattened aboveto

conform

tothecontoursof the

dome. The

outer

margin

of the whorls

is

low and

is in the

form

of a blunt acute angle.

The

base of the whorlsis flatlyarched butbluntlyangulated

where

the steep-sided

um-

bilicus begins.

The

umbilicus, about as

wide

as the whorls, is about one-third the diameter of the base of the shell.

No

traces of orna- mentation, ^if

any

existed, are preserved

on

the specimens.

Straparollus (?), species

A,

is referable to an undescribed genus seeminglyrepresentedinthe

Leonardian Bone

Springlimestone of the Sierra Diablo

by

one species

and

inthe Guadalupian

Word

limestone

No.

I ofthe Glass

Mountains by

another.

The

presentspecimens can beidentified with neitherspecies.

Figured

specimen.

— ^U.S.N.M. No.

116633a.

Horizon and

locality.

—

Spiriferellinazone,loc. 8o6f

.

90 SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. II9