332 



t'KKTACKOU.S J.A.MElJ.IHKAXClllA. 



several species wliicli are jilaecil liy all writers in the genus Iiioceramns. In this 

 respect Volriceraman is exactly coniparalile with Jcfinoceramitu (p. 268). 



A fairly complete passage can l)e traceil from T. Lamairli tn [. inruliifi(.<i. In 

 some forms of /. Lumarcld the valves l)econie more uiuMjual than usual, the left 



Fill. 9;J. — hioceramns inmhitiis. Sow. Upp:M- Chalk, locality unkuowu. British JIusoum, Xo. L21005. 



Anloiior view of left valve. x J. 



valve being relatively larger and witli less distinct folds, and the right relatively 

 less convex and its anterior area slightly concave (Fig. 85). These are connected 

 with some varieties of /. iiirohdiis by intermediate foi'ms (Figs. 8(3, 87) in which 

 the left valve possesses neai'ly all the characters of /. iiirulntiis l)ut is less curved 

 and possesses a concave anterior area, whilst on the right valve the folds are 

 almost as ]irominent as in I. iurolutus, but the flattened or concave anterior area 



