330 



MOLLUSCOIDEA BRACHIOPODA 



SUB-KINGDOM V 



Sub-Family A. TROPIDOLEPTIINAE. Schuchert. 



Terebratellidae with the loop consisting of two slender descending branches, uniting 

 with a high, vertical septum. Devonian. 



Tropidoleptus, Hall. Plano-convex plicated shells with a long straight 

 and narrow cardinal area. Teeth and dental sockets corrugated on their 

 outer surfaces. Devonian ; America, Europe, and South Africa. 



Sub-Family B. MEGATHYRINAE. Ball (emend. Beecher). 



Terebratellidae in which the loop is composed of descending branches only, passing 

 in the highest genus through stages correlative with Gwynia, Cistella, and Megathyris. 

 The lower genera do not complete the series. The original stock for the two following 

 sub-families. Jurassic to Recent. 



Gwynia, King. Minute, elongate - oval, smooth shells with a short, 



nearly straight hinge-line. Neither 

 septa nor loop. Brachia primitive, 

 consisting of a circlet of cirri. 

 Recent. 



.Zellania, Moore. Minute shells 

 without a loop, but with a median 

 septum in each valve. Lias ; Europe. 

 ,.557. Cistella, Gray (Fig. 556). Ex- 



ternally like Megathyris, but without 

 lateral septa. Cretaceous to Recent ; 

 Europe. 



Megathyris, d'Orbigny (Argiope, Deslong.), (Fig. 557). Transversely elon- 

 gate, plicate, shells with long and straight hinge-line. Dorsal valve with 

 three or five septa, causing the brachidium to have four lobes. Jura to 

 Recent ; Europe. 



Sub-Family C. DALLININAE. Beecher. 



Terebratellidae with the loop composed of descending and ascending lamellae, 



d m passing in the 



highest genera 

 through metamor- 

 phoses comparable 

 to the adult struc- 

 ture of Platidia, 

 Ismenia, Muehl- 

 feldtia, Terebrat- 

 alia, and Dallina. 

 The lower genera, 

 FIG. 550. therefore, do not 



Muehlfddtia truncata, Gemm. sp. >nrnnr/><s<i tn HIP final 

 Recent; Mediterranean. Interior P^^ esstc 



stages. 



FIG. 556. 



Cistella Ulocu- 

 laris, Desl. sp. 

 Cenomanian ; La 

 Manche. 1/1- 



Megathyris decollata, Chem. sp. 

 Recent ; Mediterranean. Interior 

 of dorsal valve, 4 /i (after Davidson). 



FIG. 558. 



Muehlfeldtia pectimculvs, Schloth. sp. Upper 

 Jura'; Engelhardsberg, Fjranconia. A-C, Shell 

 of the natural size, 

 enlarged. 



Jura to 



D, E, Two views of loop, 



of dorsal valve (c, Crura ; d, Dental 



sockets ; e, Jugum ; /, I, Ascending -,-, 



and descending branches of loop ; XvCCent. 



p, Process attached to median apnf > rst rpafrirtprl 



septum; pr, Cardinal process; S, g eneia - >- ( 



Median septum). ^0 boreal 



Platidia, Costa (Morrisia, Davidson). Small, smooth, biconvex shells with 



