1 1 8 TAL^EONTOLOG Y. 



T. Judicaricum are finei', 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 Avhicli the abdomen 



is flat, more nearly as in the adidt G. BlaJ:ei." — (A. H.) 



Local'itif and position. — Cottonwood Canon, West Humboldt Range, 



Nevada; Trias. 



Trachycebas JuDicAEicuM, Moj.sisovics. 



Plate 11, fiRs. 1, 1 a. 

 Trachtjceras Judicarictm, Mojsisov. (18G9), Jabrb. Gi'ol. Eeicb., Wien, 133, pi. 3, fig. 4. 



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

 smaller examples of T. IVIntnei/i, 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 differ from T. 

 Whitnej/i chiefly in its proportionally smaller and more crowded costre 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. Tliis, however, if of any more than indi- 

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



Locality and position. — Same as last. 



Trachvceras Judicaricum, viir. subasperum. 



Plato 11, 6g8. 2, 2 a, and 2 b. 



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

 of its costai, but differs rather decidedly, both from that shell and T. WJiit- 

 neiji, in having its costoe 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. 



