UHACHIOI'ODA. 5 



In 18.3() M. Desliaycs (Lomk. Hist. Nat. Anim. sans Vert. vii. 

 30})) proposed tlie followiiif^ arraiigement : — 

 Brachioi'odes. 



I. Valri's articulees. — 1. Producfes, Productus. 2. T^rehra- 

 tide.s, Terchratule. li. The'cidica, Thecidce. 



II. Vulrcs iibres. — 4. Liiigules, Lingule. 5. Orbiculees, Or- 

 bicule. a. Cranies, Calceola, Cranio. 



Dr. Gray in 1S40 {Synopsis Brit. Mus. 1840, i. f. 7) divided 

 the order thus : — 



Tlie family of Terehrafulidee are regular, and somewliat like a 

 Grecian lamp in form, and have therefore been called Lamp- 

 shells. The valves are articulated together, and are attached by 

 means of a tendinous l)and, which passes out of the hole in the 

 apex of the u))])er valve as in Terebratula and Sjiirifer. 



The Jjiiigulidce are attached by a tendinous tube, resembling 

 the stem of the Barnacles, which projects between the apices of 

 the gaping valves. 



The Discinidtp, on the other hand, have the tendon passing 

 out of a linear slit near the middle of the under valve. 



And at p. 155 gives a list of the genera as follows : — 



1. Lingididep, LingiUa. 2. Terehratulidce, Terebratula, Spi- 

 rifer. 'S. Product idte, Productus, Calceola. 4. Thecideida, 

 Thecidea. 5. Craniada, Crania. 6. Discinida, Discina. 



In 1841 Mr. John Phillips [Figures and Descriptions of the 

 Paleeozoic Fossils, 8vo, p. 54) arranged the genera o{ Brachiopoda 

 thus : — 



1. Valve free, attachment by exserted muscle. 



A. Valves equal. 1. Lingula. 



B. Valves unequal. 



a. Larger valves imperforate, Athyridce; * no cardinal area, 

 Producta ; ** a cardinal area, Calceola. 



b. Larger valve perforated in or under the beak. 

 Perforation reaching to the hinge-line, Delthyrida. 

 Cardinal area more or less common to both valves, Orthis. 



Cardinal area confined to the large valve. * Internal plate of the 

 larger valves separate, Spiiifera. ** Internal plates of the larger 

 valve united on the inside hne of the shell, f Plate narrow, 

 Strigocephalus. ft Plates verv' narrow, Pentamerus. 



Cardinal area obsolete, beak incurved over a minute perfora- 

 tion, which is often obtect, or merely serves to receive the beak 

 of the smaller valve, CleiothjTis. 



Perforation not reaching to the hinge-hne, Cyclothyridae. 

 * Beak truncate, perforate, Epithyris. ** Beak acute, the per- 

 foration below it, Hypothyris. 



