BRACmOPODA. 363 



i1, are found in fne Upper Oolite and tlirouglaoiit tlie Chalk 

 Rories and London Clay.* 



Family I. — Terebratxilid^. 



Shell minutely punctate ; usually round or oval, smooth or 

 striated ; ventral valve with a prominent beak and two curved 

 hinge-teeth ; dorsal valve with a depressed umbo, a promi- 

 nent cardinal process between the dental sockets, and a slender 

 shelly loop. 



Animal attached by a pedicle, or by the ventral valves ; oral 

 arms united to each other by a membrane, variously folded ; 

 sometimes spiral at their extremities. 



Fig. 147. Terebratu'a vitrca. Bora. 



Terebratula, (Llhwyd.) Brug. Lamp-shell. 



Etymology, diminutive of terehratus, perforated. 



Synonyms, Lampas, Humph. Gryphus, Muhlfeldt. Epithyris, 

 Phil. 



Types, T. maxillata, PI. XY., Fig. 1. {^ Ter. minor-sub- 

 nibra, Llhwyd. Anomia terebratula, L.) T. vitrea, Fig. 147. 



Shell smooth, convex ; beak truncated and perforated ; 

 foramen circular ; deltidium of two pieces frequently blended ; 

 loop very short, simple, attached by its crura to the hinge-plate 

 (Fig. 147, A). 



Animal attached by a pedicle ; brachial disk tri-lobed, centre 

 lobe elongated and spirally convoluted (Fig. 147, B). The 

 young of T. diphya (Pygope of Link) has bi-lobed valves 

 (PI. XY., Fig. 2) ; when adult the lobes unite, leaving a round 

 hole through the centre of the shell. 



* The author has to acknowledge his obligation to Mr. Davidson for the use of 

 the notes, drawings, and specimens, assembled during the preparation of his great 

 work on the " British Fossil Brachiopoda,' printed for the Palaeontographioal 

 Societj'; to which work the student is referred for more copious descriptions and 

 illustrations. 



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