^912 RHACOCERAS vii 



Genus, AETOMOCERAS, Hyatt 



1900, Ceph.; Eastman-Zittel, Pal. I, 575. 



" Aetomoceras, gen. nov. Type A . (Amm.) scipionianum, d'Orb. sp." 

 [Ceph. Jur. li, 7, 8]. 



Genus, CALOCERAS, Hyatt 



1870, Reversions; Proc. Boston N.H.Soc, XIV, 22, 29. 



" Caloceras torus," p. 22. " A new genus of which Caloceras torus 

 and tortilis are types," p. 29. This is the whole original description. 

 More fully dealt with in Gen. Ariet., 1889, 136 ; but no type selected. 

 Said there to be " transitional from Psiloceras to the true Arietidce." 

 But Psiloc.ras is a degenerate (smooth) derivative of a Caloceras stock, 

 and the oblique inner lobes of Psilocsras and Caloceras are not found 

 in the Arietida;, but in the Deroceratidc-e : to the latter Caloceras might 

 lead. It leads to pseudo-arietan forms with keel {Alsatites) : these have 

 very oblique inner lobes. 



Advisable to select as type A. torus, d'Orbigny. 



Result 



Genus, Caloceras, Hyatt, 1870. Genolectotype, Am. torus, 

 d'Orbigny, Ceph. Jur. liii. 



Genus, ALSATITES, Haug 



1894, Amm. Perm.; Bull. See. Geol. France, (3) XXII, 411. 



" Alsatites n. gen., type : Amm. liasicus d'Orb." [Ceph. Jur., 



XLVIIl]. 



Genus, PHYLLOCERAS, Suess 



1865, Ueber Amm.; Sitz. Nat.-wiss. CI. Wiener Akad., LII, 76. 



" Phylloceras . . Phyll. heterophyllum ist die typische form." 

 [J. Sowerby, Min. Conch., CCLXVI]. 



Genus, RHACOCERAS, Agassiz-Hyatt 



1867, Foss. Ceph; Bull. Mus. Comp. Zool., V, 86, 97. 



One of the live genera selected (named) by Agassiz (Hyatt, 71). 

 The type is inlicated by the species which bears his name : " Rhacoceras 

 heterophyllum I.. Agassiz " (p. 97), with two references " Amm. hetero- 

 phyllus Sow. Amm. heteraphyllus d'Orb. The type of the genus is there- 

 fore the same as for Phylloceras, and the name cannot be used, as in 

 this work No. 16, for the loscombei series : Hyatt's Tragophylloceras 

 covers that. 



