574 teiiebratulinjE. 



valve perforated, the foramen quite at the apex ; deltidium 

 of two pieces, often blended. Internal skeleton consisting 

 of a slender shelly loop, not attached in the middle to the 

 valve. 



Genus TEREBRATULA, Llhwyd. 



Shell usually oval and convex, smooth, ribbed, or marked 

 with radiating striae, the margins even or only slightly waved; 

 foramen complete. Loop short and simple. 



Syn. Epithyris, King, not Phillips. Gryphus, Miihlf. 

 Lampas, Humph. 



Ex. T. vitrea, Bom, pi. 130, fig. 1. Shell, T. vitrea, 

 fig. I, a, 1, b. 



In the genus Terebratula, as restricted, the loop is short 

 and simple, formed of two riband-shaped lamella? fixed to 

 the crural base, and the oral processes do not unite to form 

 a ring as in Tcrebratulina ; the " Terebratula with long 

 loops " of Davidson form the genus Waldheimia of King. 

 The recent species are but very few in number. 



Species of Terebratula. 



pulvinata, Gould. vitrea, Linn. 



uva, Brod. 



Genus TEREBRATULINA, D'Orbigny. 



Shell finely striated ; valves auriculate ; beak straight ; 

 deltidium rudimentary; foramen incomplete. Loop short, 

 rendered annular by the union of the oral processes. 



Ex. T. caput-serpentis, Linnans, pi. 130, fig. 2. Shell, 

 T. caput-serpentis, fig. 2, a, 2, b. 



In this genus the crural processes are united, forming a 

 shelly band behind the mouth of the animal, the reflected 



