J. E. GRAY. 567 



muscular impressions solitary beliind. Myostkopha. — Gen. 

 Pholas, Teredo, Aspergillum. 



" h. Elastic ligament internal : muscular impressions t\v(j, 

 anterior and posterior. Diapedastrophia. — Gen. Mya, 

 Corbula, Mactra, Nucula. 



" c. Elastic ligament external, margined ; muscular im- 

 pressions mostly two, anterior and posterior. — Gen. Solen, 

 Psammobia, Tcllina, Cyclas, Venus, Cardium, Tridacna, 

 Chama, Pectunculus, Trigouia, Unio, Area, Mytilus, Gas- 

 trochasna, Avicula. 



" d. Elastic ligament internal, not marginal : muscular im- 

 pressions one, subcentral. — Gen. Pecten, Ostrea, Anomia." 



Class VII. SpiROBRACHioPHORA.=Bracliiopoda, Cuv. 



Head none distinct : foot none for walking : arms two, 

 spiral, fringed, between the lobes of the mantle : mouth 

 between the base of the arms ; mantle two-leaved : branchia 

 lamellar, pectinated on the inner surface of the lobes of the 

 mantle : adductor muscles three or four for closing the 

 shells : shell two-valved, hinge at one end, the other end and 

 two sides open ; fixed to other bodies. Marine, breathing- 

 water. 



(«.) Shell unequivalved ; lower valve flat, affixed beneath : 



hinge none. — Criopus, Crania. 

 {b.) Shell unequivalved, peduncle tendinous coming 

 through a perforation or nick in the larger valve : 

 hinge toothed. — Terebratula. 

 (c.) Shell nearly equivalve, with a long tendinous pedun- 

 cle coming from between the apices of the valves : 

 hinge toothless. — Ligula. 



This arrangement has much of the manner of a student's 

 essay, with all its elaborate care and its harsh phraseology ; 

 but it most undoubtedly proves Mr. Gray's knowledge of 

 what was doing for Conchology abroad, and his mastery of 

 the works pviblished to advance it ; while, at the same time, 

 it contains evidence enough of much personal observation. 

 Buried at its birth in the pages of a rather obscure medical 

 journal, it remained neglected at home, and unknown on the 

 Continent, until reprinted, three years afterwards, in the 

 "Bulletin des Sciences naturelles " of the Baron de Ferus- 

 sac. Its merits as a whole are doubtful, and not consi- 

 derable enough to have gained for it any followers ; but it 

 presents a few novel views which may have had some influ- 

 ence over subsequent classifications. The method in the 

 main is borrowed from Cuvier ; but Blainville has been 



