IOP PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
surface is marked by rather large, not very well-defined ribs arranged 
in pairs. So far as can be determined, this shell has all the charac- 
ters of the right value of PD. occidentalis, which is the commonest 
Pennsylvanian species of Deltopecten and occurs associated with IZ. 
wyomingensis 1n Colorado. 
The second specimen is obliquely crushed and at present furnishes 
scarcely a clue to the original shape. The sculpture consists of some- 
what broad, flat ribs, which are strongly alternating, every other one 
being considerably larger. 
I hardly know what course to regard best in the present con- 
tingency. It seems rather probable that both specimens belong to 
the same species, and I have little doubt that one of them is the form 
better known as Aviculipecten occidentalis. Unfortunately, Delto- 
pecten clathratus antedates the description of D. occidentalis by sev- 
eral years, and it seems a pity to replace Shumard’s name by that of 
a form which was inadequately described, whose characters are not 
readily determined from the types, and of whose identity with the 
better known form there may be some, if only shght, doubt. 
Locality and horizon.—Pennsylvanian ; Wilkesbarre, Pennsylvania. 
Ty pe-specomen.—Cat. No. 33901, U.S.N.M. 
PLEUROTOMARIA ? DISTANS Lea. 
Plate XIX, fig. 4. 
1 
CO 
53. Posidoma ? distans Lea, Acad. Nat. Sci. Philadelphia, Jour., (2). 
JOG jo, AUS, JolG sore, kee, SiO, 
“ Like the above, there was but a small portion of a valve found. 
It has longitudinal strive, somewhat lke perstriata, but the striz are 
more distinct and distant, amounting almost to ribs.” 
The original of Lea’s Posidonia ? distans is such a mere fragment 
that it can hardly be stated with certainty to which division of the 
animal kingdom it belongs. It seems to be a portion of a whorl of a 
Pleurotomarioid, but nothing further can be said on that point. It 
has an irregular shape, with five gently curved, slightly converging 
lire, which are thin, rounded, and separated by flattened interspaces 
several times their own diameter. The interspaces are not of equal 
sizes, and one, possibly two, are divided by lire mueh finer than the 
others. | 
Locality and horizon.—Pennsylvanian, Wilkesbarre, Pennsylvania. 
Ty pe-specumen.—Cat. No. 33903, U.S.N.M. 
EDMONDIA ? PERSTRIATA Lea. 
JE Byss) DIDS is, By 
18538. Posidonia ? perstriata LEA, Acad. Nat. Sci. Philadelphia, Jour., (2), 
JUL, 706 FAVE, JO, 3c, ike, Bar 
The type of this species also is a mere fragment, unquestionably a 
pelecypod, probably the anterior extremity of some such form as 
