280 CARDIID.E. 



ling) couldn't get out. Another habit, however, which 

 this little cockle possesses, is more remarkable. In the 

 ' Antologia di Scienze natural!/ published at Naples in 

 1841, Sr. Costa described and figured a shell under the 

 name of C. parasitum, which appears to be a variety 

 of C. exiguum. He observes that it attaches itself by 

 means of a byssus to the boughs of trees laid down in 

 the sea for the purpose of collecting oyster-spawn. A 

 short account of these nurseries has been given in p. 46 

 of the present volume. Some interesting particulars of 

 the embryogeny of C. exiguum will be found in the 

 treatise of Professor Loven on the development of the 

 Acephala Lamellibranchiata, to which I have elsewhere 

 referred. The decided angularity of the shell serves as 

 an unfailing test to recognize this species, although (like 

 its congeners) it is subject to considerable variation in 

 respect of shape and colour. In the fry the dorsal mar- 

 gin is straight, making the outline more square than 

 triangular. 



Gmelin constituted this species from a figure in 

 Lister's c Historia Conchyliorum/ t. 317. f. 154 (" A. 

 Pectunculus exiguus, subfuscus "), which unquestionably 

 represents our shell. His own description is slight ; but 

 in adopting the name originally given by Lister he has 

 been followed by all conchologists except Donovan and 

 the authors of the * British Mollusca/ who have called it 

 pygmcenm. Among other synonyms (for variatal forms) 

 may be mentioned C. subangulatum of Scacchi, C. Siculum 

 of Sower by, C. stellatum of Reeve, and C. aquUinum of 

 Mittre*. C. parvum of Philippi appears to be also a 

 variety, and C. muricatulum of Montagu (from Walker, 

 pi. iii. f. 83, 84) the fry of the present species. 



