ANIMALS. 199 



This is a regularly formed species^ apparently identical with both the Amphidesma 

 lunulata and Cypricardia bicarinata of Count Keyserling : the former species has the 

 same pre-umbonal lanceolate depression, approximating umbones, and obliquely trun- 

 cated anterior side ; and the latter, the same granulated exterior, dorsal slope defined 

 by a faint angle running from the umbones to the posterio-ventral margin, and squared 

 posterior extremity, — as those characteristic of AUorisma elegans. 



Besides the lanceolate depression in front of the umbones, there is another behind 

 them, rather deep, and extending the full length of the hinge-margin (PI. XVI; fig. 4) : 

 neither exactly agree with what are usually termed lunette and corselet ; though it is 

 evident, they are but modified forms of these characters. 



The granulated surface of this species has some resemblance to that of AUorisma 

 gihbosa {Sanguinolario. id., J. de C. Sow., 'Min. Conch.' pi. 548, fig. 3), which, it may 

 be observed, although an allied species, has the extremities more acuminated. The 

 granules, it will be seen, by a reference to PI. XVI, fig. 5, display a tendency to fall 

 into an obliquely linear arrangement. 



The characters of the muscular impressions are represented in fig. 3, PI. XVI. The 

 pallial sinus (c) is very oblique to the ventral margin, offering, in this respect, a striking 

 contrast to that of AUorisma sulcata (PL XX, fig. 5, c). The anterior adductor muscular 

 impression {a), which is represented a little too high, has its lower border nearly 

 horizontal with the posterior angle of the pallial line. 



AUorisma elegans occurs in the Shell-limestone at Humbleton Hill, and in the lowest 

 beds at Whitley Quarry, where it is rare. Dr. Geinitz records its occurrence in the 

 under Zechstein of Thieschiitz near Gera, and Corbusen near Ronneburg. The so- 

 called Amphidesma lunulata was found in Permian Marl on the Uchta, a tributary of 

 the Wymm, by Count Keyserling, who also discovered, in the same place, the so-called 

 Cypricardia hicarinata, which is further recorded as being found in the Permian Lime- 

 stone on the Wei near Kischerma. 



Family Psammobud^ [partim), Fleming, 1828. 



Dr. Fleming made the following genus typical of the present family, — a receptacle 

 in which he also placed Astarte. Having made the latter typical of a distinct family, 

 it is herein excluded from Psammobiida, which, perhaps, embraces most of the genera 

 subsequently grouped together by Mr. J. E. Gray and others under the name of 

 Tellinida. 



Genus Psammobia, Lamarck. 



Diagnosis. — " Shell transversely oblong, equivalve, subinequilateral, slightly gaping 

 at the extremities ; surface smooth, or transversely, and more or less radiatingly 



