154 GASTROCHJENID/E. 



We have never had an opportunity of observing the 

 animal of this interesting shell in the living state. Philippi 

 has been more fortunate, and we quote his accoimt of it,* 

 and copy the figure appended : " The animal has a mantle 

 which is entirely closed, with the exception of a small 

 aperture in front for the passage of the foot. Posteriorly 

 it is extended into two siphons united for nearly half 

 their length. When I observed the animal alive the free 

 parts alone projected from the shell, and scarcely extended 

 to a third of its length. They were brown towards the 

 apertures, which were surrounded by extremely delicate 

 cirrhi. Between them the margin of each orifice is 

 striped or puckered, and nearer the interior are other 

 comb-like cirrhi, ciliated on one side. The foot, which 

 extends itself about two lines, is thin and sharply pointed. 

 I think it has a byssus." Deshayes has given some 

 figures illustrative of its anatomy in his great work on 

 the Mollusca of Algeria. 



The Mya decussata of Montagu, ov/ing to the imperfect 

 dentition of the original specimen, and its inadequate 

 representation in the " Testacea Britannica,"" has long 

 been regarded as a lost species, and even its generic 

 appellation has been at most hypothetical. The redis- 

 covery of two specimens, each by a different individual, 

 have enabled us to ascertain its identity with a petricola, 

 which, although abundant on the opposite coast of 

 France, has rarely been met with upon our own shores. 

 The larger of the examples alluded to was taken by 

 Mr. J. S. Miller, at Bristol, in clay, the other, which is 

 above the average size of the Mediterranean ones, two- 

 thirds of an inch long, and not quite half an inch at 

 the broadest part, rewarded the researches of Mr. Hum- 



* Wiegmann's Archiv. 1845, p. 1?]8. 



