1825.] Genera Anomia, Crania Orhicula, and Discina, 243 



with the eyes and nose of every subject. He has taken the 

 Linneean specific character as a generic one, or at least he 

 describes the lower valve as pierced with three holes. Lamarck 

 has adopted this genus, and referred to it a recent species, 

 which I believe to be the same, or very nearly related to the 

 following shell. 



Muller, inhis excellent work, Zoologia Danicd^h^s described 

 a shell with the name of Patella anomala, which he afterwards 

 figured with its animal, and discovered that it was furnished 

 with an under valve ; and yet for some unaccountable reason, 

 he still considered it as a Patella! Poli, in his superb work on 

 the shells of the Two Sicilies, figured a similar shell under the 

 name of Armmia turbinata^ referring it to this genus most likely 

 on account of the animal agreeing with the Linnsean character. 

 But as he always gave the animals a new generic name, he called 

 the present animal CriopuSj e»s he did that o( Anomia Epiphiiim, 

 Echion, Cuvier, from observing that the animals of these species 

 were similar to the Terebratula, and that the shell was soldered 

 to the rock immediately by the outer surface of the lower valve, 

 and not attached, as in the latter genus, by a tendon^ formed 

 them into a genus under the name of Orbicula, toking no notice 

 of the genus Crania of Bruguiere. The genus Orbiculahvis also 

 been adopted by Lamarck ; but I believe that most persons, on 

 consulting the figures of Muller, Poli, Chemnitz, and of a shell 

 described by Montague, in the Linnsean Transactions, under the 

 name of Patella distortaj which has since been discovered to 

 have an attached under valve, and stated to be an Orbicula by 

 Blainville, will agree with me^ that these shells are all the same 

 (or two very nearly allied) species, and consequently that the 

 genus Orbicula must be expunged from the system, for it is 

 nothing more than a recent species of Crania. 



Mr. G. B. Sowerby, in a paper read at the Linnaean Society 

 on March, 1818, entitled *^ Remarks on the Genera Orbicula and 

 Crania of Lamarck, with Descriptions of two Species of each 

 Genus, and some Observations to prove the P. distorta of Montague 

 to be a Species of Crania,*^ has described a shell which was 

 found on some stones which had been brought from Africa, as 

 ballast, and were used to repair the roads. This he considered 

 to be Orbicida Norvegica of Lamarck, who expressly stated that 

 the latter shell is attached by the soldering of the outer surface 

 of the lower valve to the rock, whereas Mr. Sowerby's shell is 

 affixed by means of a tendron passing through a slip in the disk 

 of the lower valve. This tendon he has called a foot ; but it 

 has no analogy with the foot of the animals of the bivalves; and 

 I believe is only a slightly modified adductor muscle. Some of 

 these shells having been sent to Lamarck, the latter formed thena 

 into a genus under the name of Discina, giving a very expres- 

 sive 2:eneric character, but being misled by receiving it fron 



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