STANTON : THE MARINE CRETACEOUS INVERTEBRATES. 37 



ceras by Sarasin, 1 who has thoroughly studied them more recently. The 

 entire absence of periodic constrictions, and the reduced number and dif- 

 ferent form of the auxiliary lobes, in the species now referred to Hatch- 

 ericeras, prevent their reference to Desmoceras. 



Another group that suggests comparison, both in general form and in 

 sutures, is that typified by the South Indian Ammonites telinga Stoliczka, 

 for which Kossmat 2 proposed the name Neoptychites, but this is somewhat 

 more involute than Hatchericeras, the whorls are more inflated, the aper- 

 ture is greatly contracted laterally, and the sutures show many differences 

 in details, especially in the proportions of the dorsal and external saddles, 

 and the first lateral lobe and the form and posture of the accessory lobes 

 and saddles. It is true that no examples showing the complete aperture 

 of Hatchericeras have been seen, but one showing a small part of the 

 body chamber gives no evidence of lateral contraction. 



The suture of Ammonites leopoldinus d'Orbigny, which is generally re- 

 ferred to Hoplites, closely resembles that of H. patagonense and the gen- 

 eral form of the adult shell is somewhat similar, though the sides are less 

 convex, the umbilicus is broader and has not the funnel shape character- 

 istic of Hatchericeras. Young shells show much greater differences in 

 both form and sculpture, Amm. leopoldinus having a row of distinct 

 elongated tubercles on either side of the somewhat flattened venter, ob- 

 scure ribs that are not developed on the middle of the flanks ending ab- 

 ruptly at these tubercles, and another row of tubercles around the umbil- 

 ical margin. The young of our new genus, which have been studied only 

 in H. argentinense, do not have the venter distinctly flattened, nor bor- 

 dered by well-developed tubercles elongated parallel with the venter. As 

 to the similarity of the sutures, Sarasin, in the paper above cited, has 

 called attention to the fact that similar sutures, suggesting a transition to 

 Placenticeras, are developed in both Hoplites and Desmoceras, and that 

 such resemblances in sutures do not necessarily mean generic identity. 

 In this connection mention should be made of the striking general 

 resemblance in the sutures of the Patagonian Ammonite and those of 

 Amm. clypeiformis d'Orbigny, which is referred by most authors to 



1 Quelques considerations sur les genres Hoplites, Sonneratia, Desmoceras et Puzosia. Bull. 

 Soc. Geol. de France, 3d Sen, Vol. XXV, 1897, pp. 760-799. 



2 Untersuchungen uber die siidindische Kreideformation, Beitrage zur Palaont. und Geol. 

 Osterreich-Ungarns und des Orients, Bd. IX, p. 165, Wien, 1895. 



