MUSEUM OF COMPARATIVE ZOOLOGY. 37 



-= Cranke Herrmannsen, Ind. Gen. Mai., I, p. 315, 1846 (as of Rang., Fer., 



and Desh. ). 

 -=; Brachiopea Rafinesque, Anal. Nat., p. 148, 1815. 



— =: Palliobranches a cog. non symmetrigues Blainville, Man. Mai., p. 515, 1825. 

 «< Fixivalcia Latreille, Syst. Regn. An., p. 205, 1825 (Ed. Berth, p. 196). 

 -=: Terebratulidea G. B. Sby., Trans. Lin. Soc, XIII, p. 469, 1822. 



Characters. Shell structure permeated with very minute tubuli. Shell 

 attached to foreign bodies by a pedicel passing through the neural valve, 

 inarticulated. Valves suborbicular, with a subcentral apex. Animal with 

 free spiral arms, with the apices of the spires directed toward the neural 

 valve. Mantle extremely vascular, fringed with long chitinous setae fur- 

 nished with setellaj. 



Synopsis of the Family. 



Genus Discina Lam. Type D. striata Schumacher sp. 1817. 



Subgenus Discina, sensu stricto. Shell with subequal externally convex valves, 

 with subcentral apices. Lower valve with a small subtriangular longitu- 

 dinal septum or prominence in the centre, with a minute circular orifice be- 

 neath it, for the peduncle, from which an impressed line or furrow extends 

 on the inside, posteriorly, for a short distance. Shell of rather solid tex- 

 ture, impunctate ; perforated by very minute tubuli (?). Type D. striata 

 Schtjm., = D. radiosa Gld., -f- D. Evansii Dav., -+- D. norvegica Sby., + 

 D. ostreoidcs Lam. 



Subgenus Orbiculoidea D'Orbigny,* = Schizotreta KuTORGA.t Shell similar 

 to the last, but with the perforation at the posterior end of the furrow, 

 which last is impressed from the outside, instead of from the inside as in 

 Discina. Type Orbiculoidea elliptica Kutorga. Dav., Int., p. 129, pi. ix, 

 figs. 253-255, 1852. 



Subgenus Discinisca D all, = Discina Auct. Lower valve more or less flat- 

 tened, concave or compressed. Upper valve more convex ; apices of both 

 subcentral or subposterior. Lower valve with a small septum as in Discina, 

 behind which is an impressed disk or area, externally concave, and inter- 

 nally elevated. This is perforated by a longitudinal fissure, extending 

 from a short distance behind the septum nearly to the posterior margin, 

 which is often slightly indented behind it. Shell more or less horny in 

 texture, minutely tubulous. Type Discina lamellosa Brod. Rve., Conch. 

 Icon., pi. i, fig. 4, 1862. 



Genus Trematis Sharp.J — Orbicclki D'Orbigny. § Shell with the upper valve 

 with a posterior apex and small false area. Lower valve flattened, with a 



* Comptes Rendus, XXV, p. 269, 1847. 



t Verh. Kais. Min. Ges., 1847. 



J Quart. Journ. Geol. Soc., No. 13. Vol. IV., p. 66, June, 1847. 



§ Comptes Rendus, XXV, p. 269, August, 1847. 



