722 CLASS xii. 



Crania RETZIUS, BRUG. Shell inequivalve, suborbicular. 

 Affixed valve plane, with four muscular impressions internally, 

 the two middle almost confluent to form one. 



Sp. Crania ringens HCENINGH., Anomia turbinata POLI, Test. utr. Sicil. 11. 

 Tab. 30, BLAINV. Malac. PI. 59, fig. 2; Mediterranean. This species is 

 commonly confounded with Anomia craniolaris L., which is fossil, like 

 many other species, from the chalk-formation. 



Compare A. J. RETZIUS Crania oder Todtenkopfs-Muschel, Scliriften des 

 Berliner Gesellsch. naturforschender Freunde, Bd. n. s. 66, SOWEKBY Trans. 

 Linn. Soc. xm. pp. 469 472, Tab. 26. 



II. Shell furnished with hinge. 



Calceola LAM. Fossil genus [of the Devonian period, DAVIDSON 

 Introduct. &c. p. 121]. 



TJiecidea DEFE. 



Terebratula LHWYD, BRUG. (species of Anomia L.). Shell 

 inequivalve, subtrigonal. Apex of larger (ventral) valve perforated 

 by a round aperture transmitting a short affixed peduncle. Hinge 

 with two teeth. Internally two calcareous branches, slender, 

 arcuate, rising from the disc of the lesser (dorsal) valve, forming 

 the support of the arms. 



[The Terebratulidce have been subdivided, in the interest of Geology, 

 into genera and sub-genera, chiefly according to the extent and form 

 of the calcareous appendage. In the true Terebratula the appendage, 

 variable in length, is formed of two riband-shaped lamellae fixed to 

 the crural base alone, and more or less folded back upon itself. 



Terebratulina D'ORBIG. The crural processes united to form 

 a calcareous band behind the mouth, and the reflected loop always 

 in front of the mouth.] 



Sp. Terebratula (Terebratulina) caput serpentis LAM., Anomia caput serpentis 

 L., Encycl. meth., Vers. PL 246, fig. 7, BLAINV. Malacol. PL 52, fig. 6; in 

 the Atlantic ocean, the North Sea, the Scottish coast. 



[Terebratella D'ORBIG. Differs from Terebratula by its loop being 

 doubly attached; the lamellae proceeding from the crural base, before 

 attaining their greatest length, sending off a flat horizontal process 

 likewise affixed to a more or less elevated longitudinal septum.] 



Sp. Terebratula (Terebratella) dorsata LAM., BLAINV. Malacol. PL 51, fig. r, 

 from the straits of Magellan, &c. 



[Megerlia KING, Krausia DAVIDSON, Morrisia DAV., Magas 

 SOWERBY, Bouchardia DAV., Agriope DELONGSCHAMPS, Megathyri* 



