CEPHALOPODA. 



41 



Clymenia. Munster. (Planulites Munst.) — Shell 

 separated from Nautilus by the partitions being slightly 

 lobed, generally only one lobe on each 

 side ; sometimes they are angularly fo- 

 liated, but not toothed ; the siphuncle 

 is very small, and always passes near 

 the inner edge of the partitions; the 

 back is rounded and the umbilicus 

 remote, so that all the sutures are seen aymen ia striata. 

 on each side. — 43 species, fossil. 



Gyroceras. Meyer. — Shell many-chambered, rolled 

 on a plane, regularly spiral, but the 

 whorls not touching each other ; the 

 partitions are regular, with simple 

 symmetrical edges ; the last cham- 

 ber is very large, at least forming 

 the third part of the last whorl ; the 

 siphuncle is very thin, connected 

 and sub-dorsal; the mouth is oval, sometimes angular. — 17 

 species, fossil. Woodward says the siphuncle is radiated. 



Lituites. Breyn. — Shell many-chambered, at first 

 spiral, rolled on a plane, the whorls either touching or free, 

 the last chamber large and produced in a straight line ; 

 the partitions stand obliquely, having simple edges, and a 

 ventral siphuncle ; the mouth orbicular, simple, or with 

 notched edges. — About 15 species, fossil. 



Trocholites Hall, Philippi mentions as a sub-genus. 



Ascoceras. Barrande. (Cryptoceras Barr.) — This 

 new genus of the Nautilacea was made on account of the 

 peculiar situation of the chambers ; they are not perpendi- 

 cular to the axis of the shell, but almost parallel to it ; and 

 the chambered portion of the shell embraces that part 

 which is not chambered. 5 species, fossil. 



