J. W. Jackso7i — TJte Brachiopod Liothyrella. 77 



notable feature of this species is the excessive thickening of the 

 hinge-processes and muscular fulcra generally. This fact renders 

 it a somewhat difficult matter to define the type of cardinalia. 

 I fortunately possess one specimen in which the calcification has 

 not progressed so far as usual: this Shows botli cardinalia and 

 hrachidium. The crural bases in this are well-defined and consist 

 of fairly broad plates set almost vertically to the slight hinge- 

 plates uniting them Avith the high-standing socket-ridges. The 

 hinge-plates unite along the middle line of the crural bases, the 

 latter having a well-defined ventral and dorsal edge. 1 have seen 

 no junction like this in nnj recent Ziothyrma ; nor is it present in 

 the Crag or London Clay Terebratulce. There is a prominent 

 cardinal process at the apex of the valve ; also a thin hair-like 

 mesial septum in the umbonal cavity. Both the cardinal process 

 and mesial septum become more definite in the thickened specimens. 

 The crura are broad and sliort ; the descending branches and trans- 

 verse band of the loop are also broad, and the latter is sharply bent 

 ventral wards in the middle. The junction of the descending branches 

 with the transverse band is sharply angulated. Figures of the interior 

 of T. carnea are given by both Davidson ' and Quenstedt.^ 



Before proceeding it might here be appropriate to point out that 

 the hrachidium of the Crag Terehratulce differs from that of T. carnea 

 in being relatively wider with a narrow transverse band not sharply 

 bent ventrally, and in having much sharper points at the extremities 

 of the descending branches. It has also longer crural points.^ In 

 general characters it resembles that of the recent L. uva, but not 

 that of Z. vttrea.^ 



The cardinalia and hrachidium in recent Liothyrince exhibit some 

 interesting features. The type seen in L. uva and closely allied 

 forms differs somewhat from that of the genotype, JO. vitrea, and 

 very materially from that of L. stearnsi or L. bartletti. The extremes 

 are clearly seen in Blochmann's figures (op. cit., 1908, pi. xxxix). 

 In L. uva the whole structure is of a short triangular form, and the 

 transverse band of the loop is very narrow. The junction of the 

 descending branches with the transverse band is sharply pointed. 

 The crural points are close in. Between the socket-ridges and the 

 ill-defined crural bases is a narrow curved plate. There is a thin 

 mesial septum. In L. stearnsi, on the other hand, the structure 

 consists of long, almost parallel, descending processes, and the 

 transverse band is very broad; it is also sharply bent ventralwards 

 in the middle. The clmracteristics of X. stearnsi are taken from 

 Blochmann's figure (op. cit., 1908, pi. xxxix, fig. 29). L. vitrea 

 and some others appear to agree closely with this form. In general 

 the crural bases, which are not very marked, are well separated 



^ Monog. Brit. Cret. Brack. (Pal. Soc), 1854, pi. viii, figs. 2, '2a. 



^ Petrefactenkunde Deutsch., II. BracMo;poden, Leipzig, 1871, pi. xlviii, 

 fig. 42. 



•'' This is based upon the figure given by Davidson, Suppl. Tert. Brack. 

 (Pal. Soc), 1874, pi. ii, fig 1, and upon imperfect specimens of my own. 



* The ovate outline and broad dorsal uniplication of the Crag shells also 

 show greater affinity with L. uva. 



