780 Report or THE State GEOLOGIST. 
their inner faces, not making the nooses peculiar to AruyRris 
proper ; they are broad and blade-like, narrowing beyond the 
insertion of the jugum; the jugum is situated posteriorly ; the ac- 
cessory lamellz are narrow near their origin, broaden and then 
taper again, having the shape of a sickle. The spiral ribbon 
Fic. 312.— The fimbriated spirals of Cliothyris pectinifera, Sowerby (sp.). (Davipson.) 
appears, from the figures given by Davipson and Krne, to be 
pectinated on all its outer edges, but it has not been shown that 
the anterior extremity of the jugum is similarly ornamented 
(Type, Cliothyris pectinifera, Sowerby (sp.). Lower Carbon- 
iferous — Permian.) 
Subgenus Actinoconchus, McCoy. 1844. 
Shells characterized by the extravagant development of the 
concentric lamellar expansion, which are striated radially by dis- 
tant sulci. These expansions appear to be actually fine, tubular 
spines connected by, or imbedded in a tenuous calcareous plate. 
The interior of the pedicle-valve bears a median septum which 
traverses the pedicle-cavity and half the length of the shell; 
also two strong dental plates which are continued forward, 
slightly diverging, for more than one half the length of the sep- 
tum. Mr. Davinson has given elaborate illustrations of the spirals 
and loop of this species, from preparations by the Rev. Norman 
Guass, and from them it appears that the latter organ, the 
jugum, has essentially the same conformation as in Cliothyris 
pectinifera, though placed further forward. The saddle of the 
32 
