10 BRACHIOPODA. 



Uncites, DefTaace"? ; TrigonosemuSjKcemg; E%ncAo7-a, Dalman; 

 Pygope, Link ; Delthyrideea, M'Coy ; Pentamerus, Sowerby. 



Order IV. Sarcicobrachia. 



The oral arms fleshy to the base and without any shelly sup- 

 port ; the lower valve without any processes on the hinge-margin 

 or disc, or except sometimes a slight medial longitudinal elevation. 



Fam. 1. Productidce 



consists entirely of fossil species, some much resembling those 

 of the former family, but the shells are generally spinose ; they 

 are only attached to marine bodies by the surface of the ventral 

 valve, as the genera Productus, Sow. ; Strophalosia, King ; Cho- 

 netes, Fischer; Leptcena and Orthis, Dalman; Strophomena, 

 Rafinesque ; and Calceola, Lamk. This family comprises Mr. 

 King's Productidce, StrophomenidcE and Calceolidce. 



Fam. 2. Craniadce. 



Nearly allied to the last, but the upper valve is simply conic 

 like Patella, and the animal is attached by the outer surface of 

 the ventral valve. 



The animal has been figiu-ed by Miiller, PoH and others. It 

 includes the recent genus Crania of Retzius, including the Or- 

 bicula of Lamarck, Criopus of Poll. The lower valve of the only 

 recent species I am acquainted with varies greatly in thickness 

 and form according to the position and habitation of the animal. 

 This animal in many particulars is alhed to Thecidaadte. 



Fam. 3. Discinidce. 



The upper valve is conical and patelloid, the lower orbicular, 

 and is attached to marine bodies by a short tendinous pedimcle, 

 which passes out through a slit in the hinder part of the disc of 

 the ventral valve. 



The animal of this genus has been described by Mr. Owen 

 under the name of Orbicula, Mr. G. B. Sowerby having some 

 years ago confounded this shell with that genus, which has caused 

 confusion, which has existed to this day. The shell was first de- 

 scribed by Schumacher as a section of the genus Crania. Mr. 

 King, probably misled by this mistake, does not include it in his 

 arrangement. This shell is peculiar, for being homy rather than 

 a shell texture, it is flexible when moist. 



Fam. 4. Lingulidce. 



The valves are nearly equal elongate, and supported by a thick 

 peduncle which comes out between the beaks of the two valves. 

 The shells are covered with a homy periosti-aca, and in some 

 species the shelly matter is so very thin that the shells are flexible 



