2 58 JAMES PERRIN SMITH AND STUART WELLER 



Fi°"s. i a-c. In Hedenstroemia, as denned by Waagen, 1 the ventral lobe is 

 divided, the external saddle divided by adventitious lobes ; the first four 

 lateral lobes are serrated, and there is a series of about six pointed auxiliary 

 lobes. The form is flattened, involute with narrow and angular abdomen. 

 No keel is known, and the shell is smooth. In Prodromites the ventral lobe 

 is undivided and the external saddle is entire and rounded ; but in the serra- 

 tion of the first four or five lateral lobes and in the auxiliary series it is almost 

 identical with Hedenstroemia, as also in the form, with the exception of the 

 keel, which may not have been preserved on the few specimens known. 

 There can be no doubt that these two genera belong to the same family, and 

 even subfamily, in spite of the long time that intervened between the Kinder- 

 hook formation of the Lower Carboniferous and the Lower Trias. Heden- 

 stroemia, according to Waagen, 1 belongs to the Pinacoceratidae, subfamily 

 Hedenstroeminae, which also contains Clypites Waagen, and Camites Mojsi- 

 sovics, of the Lower Trias. The family Pinacoceratidae in the broader sense, 

 as defined by Waagen {op ciL, p. 139), contain all forms with compressed 

 involute whorls, many lateral lobes and saddles, and an auxiliary series of 

 lobes outside of the umbilicus. In this family belong the following sub- 

 families : (1) Medlicottinae, (2) Beloceratinae, (3) Beneckeinae, (4) Heden- 

 stroeminae ; all of which have representatives in American Paleozoic or 

 Triassic strata. 



It is not likely that Prodromites is a descendant of Beloceras, since the 

 septation is quite different in the two genera ; and unless Hedenstroe?nia 

 should be found to have a keel, it is not likely that it has descended from 

 Prodromites. Beloceras is commonly placed under the Prolecanitidae, 

 although it antedates any typical species of Prolecanites. On the other hand, 

 Medlicottia, which is closely related to Prodromites, seems certainly to have 

 been a descendant of the typical Prolecanitidae. No solution of these ques- 

 tions is possible until the ontogeny of several of these genera is known, which 

 is prevented at present by a scarcity of specimens. Until other evidence is 

 forthcoming, Prodromites is placed in the family Pinacoceratidae, subfamily 

 Hedenstroeminae. 



This genus is not founded solely on Miller's figure, which is not accurate, 

 nor even on his type specimen, but also on three other specimens of this 

 species, and one of another species, bringing out certain characters that did 

 not show on Miller's type. 



The writers have had at their disposal for study four specimens of 

 Prodromites gorbyi Miller, and one of P. ftraematurus S. and W., all of 

 which, except one, belong to the paleontological collection of the Walker 



'Pal. Indica. Salt Range Fossils. Fossils from the Ceratite Formation, p. 140. 



1 Pal. Indica. Salt Range Fossils, Vol. II. Fossils from the Ceratite Formation, 

 p. 140. 



