MUSEUM OF COMPARATIVE ZOOLOGY. 95 



Coeloceras mucronatum Hyatt. 



Amm. mucronalus D'Orb., Terr. Jurass., Ceph., p. 328, pi. I'M. fig. -1-8. 



Loc. Whitby, Milhaud, Laumiere, Mende in Lozere, Donau-Main Canal, 

 Salins in Jura, Pres d'Avallon, Montpellier ; Coll. Dr. Krantz, L. de Ko- 

 ninck, Prof. Bronn, and M. Boucault. 



Dactylioceras* Hyatt. 



The abdomen is either equal in breadth, or less than the back, instead 

 of being broader than, or equal in breadth to, the baek, as in the preceding 

 genera. The lateral pilae in the adult are smooth and invariably single ; 

 the abdominal pila? may be either bifurcated or single. The young have 

 the same development as the young of Coeloceras crassum, but the tubercles 

 are dispensed with before the adult state is attained. (The tubercles are 

 hardly distinguishable in the young of some species, such as Holandrei and 

 Braunianum, especially on the fossil easts, but are, nevertheless, present in 

 all the shells.) Septa do not differ materially from those of the preceding 

 genus, except perhaps in the greater simplicity of the lobes and cells, which 

 are hardly so close together or so complicated. 



Dactylioceras commune Hyatt. 



Amm. communis Sow., Min. Conch., v. 2, p. 9, pi. 107, fig. 23. 

 Naut. annularis Rein., Naut. et Arg., p. 79, pi. G, figs. 5G, 57. 

 Amm. annularis Ziet. Verst. Wiirt., p. 14, pi. 10, fig. 10. 

 Loc. Whitby, Boll, Amberg, and Langenbriicken ; Coll. Dr. Krantz, L. 

 de Koninck, and Prof. Bronn. 



Dactylioceras Holandrei Hyatt. 



Amm. Holandrei D'Orb., Terr. Jurass., Ceph., p. 330, pi. 105. 

 Loc. Whitby, Cheville in Sarthe, Fontaine Etoupe Fours in Calvados ; 

 Coll. L. de Koninck and M. Boucault. 



Dactylioceras annulatum Hyatt. 



A?nm. annulalus Sow., Min. Conch., v. 3, p. 41, pi. 222. 

 Amm. annulalus D'Orb.. Terr. Jurass., Ceph., p. 2G5, pi. 7G, figs. 1, 2. 

 Argo. anguinus Rein., Naut. et Arg.. p. 89, No. 1, pi. 12, fig. 73. 

 Amm. cequistriatus Ziet., Verst. Wiirt., pi. 12, fig. 5. 

 Loc. Whitby, Illminster, St. Amand, Fontaine Etoupe Fours ; Coll. L de 

 Koninck and Dr. Krantz. 



Dactylioceras Braunianum Hyatt. 



Amm. Braunianus D'Orb., Terr. Jurass., Ceph., p. 327, pi. 104. 

 Loc. Milhaud and Plateau de Larzae ; Coll. L. de Koninck and Dr. 

 Krantz. 



* AaKTvXios, a ring. 



