TEREBRATULA. 



TESTA iiiaBquivalyis, aequilatera, ovalis vel sub-' 

 trigona, pediculo brevi^ tendineoque affixa; 

 valvse alterius umbo productus, ssepe incurvus, 

 apice perforate aut emarginato; cardo dente in 

 titroque latere unico; valva altera processibus 

 duobus testacei^, gracllibus, plerumque fur- 

 catiS) varie flexuosis, e cardine naseentibus 

 intern^ instructa. Impressiones musculares in 

 valva perforata duse (interdum sed rariiis dis- 

 tinetsBj) oblongge, centrales, approximatae; duae 

 itidem in altera rotundato-subtrigonge^ subcen- 

 trales, distantiores. 



The principal and most numerous Genus of Lamarck's 

 family of Brachiopoda, all of which are furnished with 

 two shelly valves, attached to rocks and submarine bodies 

 either by a byssus or tendinous pedicle, or by the outside 

 of one of the valves, and remarkable for two long opposite 

 fringed arms, that are rolled up into a spiral form when 

 at rest. To this family belong not only the Orhicuta, Tere- 

 bratula and lAngula, which Lamarck includes in it, but 

 also his Crania and Calceola^ Sow"erby's Spirifer^ Defrance's 

 Thecidea, and Hipponyx, which we are surprised to find 

 still arranged by Lamarck among his Cali/ptraciens under 

 the singular appellation of Cabochons (Pileopsis) ay ant 

 un support connu;" we thought we had sufficiently de- 

 monstrated the impropriety of this, but in order to show- 

 it more clearly we have only to observe that Lamarck's 

 Calyptraciens are Gasteropodes, that the shell being a testa- 

 ceous deposition from the mantle, and the Gasteropodes, 

 not being furnished with such a mantle under their foot^ 



