118 PALEONTOLOGY. 



t. Judicaricum are finer, and the abdominal channel appears at a much 



earlier period of the shell's growth. The abdominal channel in this species, 



and others of the same genus, is preceded by a stage in which the abdomen 



is flat, more nearly as in the adult G. BlaJcei." — (A. H.) 



Locality and position. — Cottonwood Canon, West Humboldt Range, 



Nevada; Trias. 



Trachycekas Judicaricum, Mojsisovics. 



Plate 11, figs. 1,1a. 



TracJiyceras Judicaricum, Mojsisov. (1869), Jabrb. Geol. Eeich., Wien, 133, pi. 3, fig. 4. 



The specimens ranged under the above name agree so nearly with the 

 smaller examples of T. Whitneyi, Gabb, that I had only separated them as 

 a variety of that species. Professor Hyatt, however, whose facilities for 

 making critical comparisons of this group of fossils with European forms 

 are far superior to my own, thinks it identical with the above-mentioned 

 foreign species. As may be seen by our figure, it seems to difier from T. 

 Whitneyi chiefly in its proportionally smaller and more crowded costse and 

 nodes. Mr. Hyatt sent me the following note'in regard ,to its relations to 

 Mojsisovics' species: 



" The only difference noticeable in Mojsisovics' description is that the 

 pilse are continuous across the abdomen, whereas in this specimen the 

 abdominal channel is smooth. This, however, if of any more than indi- 

 vidual value, is probably a local variation." — (A. H.) 



Locality and position. — Same as last. 



Trachyceras Judicaricum, var. subasperum. 



Plate 11, figs. 2, 2 a, and 2 b. 



This shell agrees with the last in form, proportions, and the smallness 

 of its costse, but differs rather decidedly, both from that shell and T. Whit- 

 neyi, in having its costse almost entirely obsolete around the middle of each 

 side, and only a single row of rather distant prominent nodes there. It shows, 

 however, a tendency to develop a small row around the umbilicus on each 

 side, as in those forms, and has the usual row of oblique nodes on each side 

 of the mesial furrow of the periphery, with another row a little farther in. 

 At least this is the character of the single specimen of this kind in the col- 

 lection, as may be seen by our figures of it on plate 11. 



