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to the modifications of Lituites and Ancistroceras. It is completely 

 uncoiled in the young, and the tip or apex has not even the open 

 coiling of Ancistroceras, but is really an open or cyrtoceran curve. 



The annuli of the shell are also simpler in curvature and accord- 

 ing to Remele they have low broad dorsal and ventral crests and 

 corresponding low broad lateral lobes. These phylogerontic curves 

 appear to be acquired in the early ephebic stages, and therefore ap- 

 pear earlier in the ontogeny than in Ancistroceras. 



The siphuncle is large and may be either dorso-centren, or about 

 centren, and in R. Beyrichea is said by Remele to be nearer to the 

 venter than to the dorsum or ventrocentren. 



The list of species given by Remele* is as follows : R. Beyrichia, 

 Zaddachi, Oelandicum, damesi, t emu striatum. 



Rhynchorthoceras (7) dubium. In the Dyer collection, Museum 

 Comparative Zoology, there is a fragment that shows this genus 

 probably occurs in the Niagara group of Indiana, but the younger 

 stages are wanting and it cannot be surely placed here until these 

 are known. The first part of the free volution has the usual bands 

 of growth with hyponomic sinus, these lines inclining orad and 

 without inflections or with hardly perceptible lateral sinuses to the 

 dorsum where they unite in low, broad saddles. 



There are also three inconspicuous low, broad costae on this part 

 of the shell. The form is a slightly compressed ellipse, the siphun- 

 cle large, ventrocentren, the sutures have ventral and dorsal sad- 

 dles and lateral lobes. The growth bands lose their inclination in 

 the older part of this volution, becoming straighter on the sides 

 and the hypomic sinus almost disappears. This last characteristic 

 seems to place these fossils in this genus. 



Holmiceras, n. g. 



Lituites prazcurrens sp., Holm, has open, discoidal whorls, like 

 those of Angelinoceras latum, and closely resembles this species in 

 form and proportions, both of the enrolled and outstretched whorls, 

 but the lines of growth and annulations are very distinct. It has 

 the four major sinuses in the lines of growth, as in Lituites, but the 

 median dorsal crest is absent. The aspect shows the presence of 

 another genus in this family and the sutures are also different from 

 those of Lituites, having distinct ventral and dorsal lobes in the 

 ephebic stage, with low, broad, almost straight, lateral saddles. 



*Zeitsch. Deulsch. Geoi. Gesell., xxxiv, 1882. 



