388 



MOLLUSCOIDEA 



PHYI UM V 



Numerous, laterally directed, brachial ridges in the ventral valve, with corre- 

 sponding divergent grooves in 

 the median region of the dorsal 

 valve. Permian ; China and India. 

 Oldhamia Waagen (Fig. 572). 

 Differs from Leptodiis in that the 

 ventral valve is sub-hemispherical 



i'^S^^Sm^^^:^ with the incurved apex covered 

 ^^^f^^^^n by a callosity, as in BelleropJion. 



Fio. 572. 



Permian ; India and China. 



Loczyella Freeh. Said to be 

 like Leptodiis, but without the 

 brachial ridges. May not be a 



Oldhamia deoipiens Waagen. Productus Limestone ; Salt -r, t • i *"* tt n t • 



Range, East India. A, B, Interior of ventral and dorsal brachiopod. Upper UarbOni 



valves, respectively (after Waagen). j ^^^^^ . banking, China. 



Subfamily B. Thecidiinae Dall. 

 Thecidiidae with the brachial markings restricted to the dorsal valves. 



Thecidea Defrance (Thecidium Sowerby) (Fig. 573). Dorsal brachial im- 

 pressions with three pairs of symmetrical lobes, radially directed. Cretaceous. 



Thecidea and the following genera of the subfamily Thecidiinae comprise for the 

 most part small, sometimes extremely minute forms, represented from the Trias to 

 the present day ; the climax of diversity occurred in the Cretaceous. 



Lacazella Munier-Chalmas (Figs, 574, 575). Dorsal brachial impressions 



Fig. 573. 



Thecidea papiUata Scliloth. Upper 

 Cretaceous; Ciply, Belgium. J, £, In- 

 terior of ventral and dorsal valves, re- 

 spectively, 2/j (after Woodward). 



Fir,. 574. 



Lacazella vermiciilaris 

 (Schloth.). Upper Cretaceous ; 

 Maestriclit. Dorsal valve, 2/j 

 (after Suess). 



Fig. 575. 



Lacazella inediter- 

 ■ranca (Risso). Re- 

 cent. Interior of 

 dorsal valve showing 

 braehia, % (after 

 Woodward). 



with two or three unequal pairs of lobes, medially directed. Jurassic to 

 Recent ; Europe. 



Thecidiopsis Munier-Chalmas (Fig. 576). The two large, dorsal, brachial 

 impressions each have four pairs of lobes 

 laterally and medially directed. Creta- 

 ceous ; Europe. 



Thecidella Munier-Chalmas. Dorsal 

 brachial impressions simple, anteriorly 

 directed. Jurassic; Europe. ,„..,„,„^„ ^ ,. 



F.'}idp<iplhi MnniPT- Chalmas Trans- on tiie Rlihie. yi', borsaf aspect. 7j, C, Interior 



£juaeseua lVlUniei-l.^naimab. J-I^'/^ of ventral and dorsal valves, respectively, Vi- 



verse shells in which the dorsal brachial 



impressions have three pairs of simple lobes antero-laterally directed. Jurassic; 



Europe. 



Fig. 576. 

 Thecidiopsis digltata{Go\AL). Greensand ; Essen 



