60 PHOLADID^. 



hart, remarkably resembles that of the tunic in the genus 

 Asc'idia. The gills themselves are very peculiar, present- 

 ing the appearance of long, brown, fleshy cords ; so different, 

 indeed, from the usual appearance of those organs, that Sir 

 Everard Home mistook portions of them for male repro- 

 ductive bodies, and Sellius and Delle Chiaji for the ovaria, 

 misled in part by finding the eggs lodged there after pro- 

 trusion. The true ovarium is a bright white, fatty, cylin- 

 drical body, placed in the main mass of the viscera. The 

 heart, as Professor Van Beneden has shewn, is placed quite 

 distinct from the intestine, and is not pierced by the latter. 

 The circulating system is extremely simple. The blood was 

 stated by Home to be red, but this is denied by recent ob- 

 servers. The mouth is furnished with labial processes, and 

 internally with a curious cartilaginous club-shaped body, 

 which is peculiar to the Teredo^ but may possibly be analo- 

 gous to the tongue of higher Mollusca. The oesophagus is a 

 long thin tube, furnished with a salivary gland ; there are 

 two distinct stomachs, one of which is invested with the liver. 

 The foot is very rudimentary, and shaped like a sucker, 

 so that Deshayes, we think wrongly, describes the animal as 

 having no foot. The anterior adductor muscle is strongly 

 developed, and the posterior but slightly, so as to leave 

 scarcely any traces in the shells. The presence of two cal- 

 careous styles, called "pallettes" by Adanson, "calamules" 

 by Deshayes, in the muscular ring which surrounds the base 

 of the bifurcating extremities of the siphons, is a remarkable 

 feature, and, as will be seen in the following descriptions of 

 the species, one of no small importance as a source of spe- 

 cific distinction. 



On the ground of the many peculiarities of the anatomy 

 of Teredo, M. Deshayes has constituted it the type of a 

 distinct family. Nevertheless, the relations of this genus 



