210 CAEBOXIFEEOrS CEPHALOPODA OF IRELAND. 



GiTPHiocERAS r sp. Plate XLVIII, figs, o n, }i. 



This small fragment of a rather Avidely umbilicated shell, the inner whorls of 

 which are minutely and regularly striated transversely, is very difficult to determine 

 specifically. It bears some resemblance to G. fsfenoJohnm, J. Phillips, but the 

 uml>ilicns is proportionally larger, and it is a more inflated shell than the latter. 

 As I cannot recognise in it the .young of any species knowni to me I have not 

 ventured to name it. 



Si/nopai.i of FixmUies, Genera, avd Species contawerl in flm Mnnofjrnph, iviili 

 ileacripiinns of the Families and Geneyn ; f]ie new itpecies worked irith an 

 asterislc. 



811E-0RDEU— XAUTILOIDEA. 



FamiJij — OKTnncETJATiD.T:, M'Coi/, 1844. 



Longicones and Brevicones, with cyhndrical siphuncles and widely separated 

 septa. Body-chamber large ; aperture with an entire peristome. 



Genus Okthoceuas {Breyn, 1732). — Shell straight or slightly curved ; elongate- 

 conical ; circular or subelliptical in cross-section. Septa concave, usually horizontal, 

 sometimes slightly obliijue. Siphuncle of variable dimensions ; cylindrical ; central 

 or excentric ; calcareous deposits sometimes present. Septal necks short or 

 reaching to the next septum. Body-chamber large ; aperture entire, scarcely ever 

 contracted ; sometimes with a constriction below it. Surface of test frequently 

 with transverse or longitudinal ornaments (aunulations, ribs, strise, etc.). 



Cambrian to Trias. 



A. Longicones. 



I. Group L.«viA. (Species with smooth test.) 



Suh-groiip Cylindritormes. {Species with cylindrical siphuncle.) 



1. Orthocenis Leinsterensc* 



2. ., variabile.* 



3. ,. Colei.* 



4. ., Nolani.* 



5. .. Sandi-Doulafthi.* 



6. ,, acre.* 



13. Orthocei-as perapproximatimi.* 



