302 REPORT UNITED STATES GEOLOGICAL SURVEY. 



shells of Southern India which are evidently congeneric with this species. 

 Apparently entertaining similar doubts, Mr. Whiteaves referred with 



doubt a shell that is probably congeneric with ours to Martesia (Marte- 

 sia ? carinifera, Geol. Surv. Canada, Mes. Foss. part 1, p. 54, pi. ix, fig. 7.). 



Parapholas mersa Stoliczska, from Cretaceous strata of Southern In- 

 dia, possesses all the generic characteristics of this shell (Paheonto- 

 logia Indica, vol. iii, p. 24, pi. ii, fig. 7). It differs from this species too 

 obviously to need minute comparison, but it may be mentioned that 

 our shell is much more slender, its umbonal grooves more oblique, its 

 front not so much impressed, and its basal accessory valve is shorter 

 and sharply pointed in front instead of behind. Mr. Whiteaves was not 

 able to learn anything concerning the accessory valves of his species. 

 The presence of two umbonal grooves, together with its elongate form, 

 would seem to indicate generic relation with our shell. In its specific 

 characters it differs widely from all known" species, except, perhaps, Mar- 

 tesia cuneata Meek & Hayden. Some examples apparently of this species, 

 collected in the valley of the Yellowstone Elver by Mr. J. A. Allen, indi- 

 cate that the full adult forms are a little more elongate than the type-speci- 

 mens of that species, and in that respect, as well as in many details, they 

 closely resemble our species. They have, however, only one umbonal 

 groove. Another feature of close resemblance between that species and 

 ours is the almost exact identity in shape, size, and position of the umbo- 

 nal plate, and its division by a linear longitudinal suture in both species. 

 It thus seems that the division of the umbonal plate is not a generic 

 character, but I can hardly agree with Dr. Stoliczska that the shells 

 having two umboual grooves are not generically distinct from those with 

 one. 



Position and locality. — Cretaceous strata, probably of the age of the 

 Colorado Group ; Upper Kanab, Southern Utah, where it was collected 

 by Maj. J. W. Powell. 



GASTEROPODA. 



Genus PALIUEUS Gabb. 



Paliueus pentangulatus (sp. nov.). 



Plate 4, figs. 4 a and h. 



Shell slender, somewhat strongly bent, very gradually tapering from 

 the proximal to the distal end ; longitudinal angles or carinas five, prom- 

 inent, subangular; intervening grooves broadly concave ; internal cav- 

 ity moderately large, circular in cross-section. 



Full length unknown; the only example collected, which is appar- 

 ently nearly full-length, 17 millimeters ; diameter at the proximal end 

 of the specimen 2 millimeters, at the distal end li millimeters. 



This shell has much the aspect of a portion of the stem of a Penta- 

 crinus, especially as to its pentangular cross-section, but it is destitute 

 of the jointed structure of those bodies, and the circular internal cavity 

 shows plainly its testaceous character. It seems evidently to belong to 

 the same group to which Mr. Gabb gave the name Paliurus, although it 

 is marked by five instead of by only three carina?, as in the typical 

 species. 



I am much more inclined to think these shells are related to Dentalium 

 than to the Annelid®, to which Mr. Gabb referred the typical species. 

 Therefore they are so classified in this paper. 



