MUSEUM OF COMPARATIVE ZOOLOGY. 10 



Ophioceras * Hyatt. 

 Keel constant, sometimes obscure. The shell has a greater number of 

 whorls than in the preceding genus, because the young increase more 

 slowly in size. Pilae straight, depressed ; appear at an early stage in the 

 young, and are well defined upon the second whorl. Umbilicus open ; 

 sides exposed. Abdominal lobe deeper and narrower than the lateral 

 lobes. Superior lateral lobes broad, shallow, and but very little longer- 

 than the inferior lateral. The auxiliary lateral lobes are cuneiform, and 

 incline toward the umbilicus. 



Ophioceras torus Hyatt. 



Amm. torus D'Orb., Terr. Jurassique, I., p. 212, pi. 53. 

 Loc. Semur, Quedlinburg, ltinteln, and Schauniburg ; Coll. Boucault, 

 Dr. Krantz, and De Koninck. 



Ophioceras raricostatum Hvatt. 



Amm. raricostatus Ziet., Verst. Wiirt., p. 18, pi. 13, fig. 4. 

 Amm. raricostatus Quens'dt, Der Jura, p. 105, pi. 13, figs. 16-18. 

 Loc. Semur, Boll, and Balingen, Wiirtemberg ; Coll. Boucault, Dr. 

 Krantz, Mus. of Stuttgart, and De Koninck. 



Ophioceras Johnstoni Hvatt. 



Amm. Johnstoni Sow., Min. Conch., v. 5, p. 70, pi. 449. 

 Amm. arietis Ziet., Verst. Wiirt, p. 3, pi. 2, fig. 4, but not figs. 2 and 3.f 

 Amm. raricostatus D'Orb., Terr. Jurassique, I., p. 212, pi. 54. 

 Loc. Lyme Regis, Semur, and Balingen ; Coll. Wright, Damon, Bou- 

 cault, and De Koninck. 



Ophioceras kridioides Hyatt. 



Loc. Basle ; Coll. Prof. Bronn. 



Abdomen like that of 0. Johnstoni, but rounder than in 0. raricostatus, 

 and the young increase more rapidly than in either of these species. The 

 pike are most prominent near the abdomen, and in the young they are 

 more numerous than in the adult, numbering about twenty-four on the 

 third whorl, and about twenty on the fifth whorl. 



Abdominal and superior lateral lobes broad and shallow, the latter 

 equally divided. There are two pointed auxiliary lobes on each side.', and 

 the superior lateral cells are equally divided. 



Ophioceras commiscens Hyatt. 



Loc Lyme Regis ; Coll. B. M. Wright. 



* *O0u, a serpent. 



| Figs. 2 and 3 nre identical with Discoceras spiratissimus IJi/att (Amm. spiratia- 

 simus Quens'dt). 



