258 CARDITID^E. 



above-named, I feel satisfied that the two species from 

 the extremities of the Atlantic Ocean ought to be in- 

 cluded in the same genus. Perfect specimens of C. ant- 

 arcticum are closed at both ends ; and the ligament is as 

 much exposed, and the lateral teeth are as fully deve- 

 loped, in that species as in the other. 



There is, however, a much greater difficulty as to the 

 position and relations of this anomalous genus, in con- 

 sequence of the following description of Turtonia in the 

 ' British Mollusca ' (vol. ii. p. 80) : " Animal with the 

 mantle widely open anteriorly, a single very slender 

 siphonal tube at the shorter end, and an ample and 

 strong foot angulated at its posterior base proceeding 

 from the longer " The authors also state in the descrip- 

 tion of the species, " all we know of the animal is con- 

 tained in the generic character, due to the observations 

 of Mr. Alder." The representation of the animal, given 

 in pi. O. f. 1. of that work, corresponds with the above 

 description. In the ' Supplementary Notes on the 

 Acephala' (vol. ii. p. 375), and in the description of the 

 plates (vol. i. p. 480), a material error is noticed as to 

 the engraving, viz. in the " siphon projecting from the 

 short, instead of the long, end of the shell." The de- 

 scription remains uncorrected. Mr. J. de C. Sowerby 

 assured me that he accurately made the engraving from 

 a sketch furnished by the late Professor Forbes, whose 

 name as the draughtsman appears on the plate. I 

 thereupon wrote to Mr. Alder for further information ; 

 and in reply he says, ' ' I am quite certain of Turtonia 

 minuta (the species in question) having a small slender 

 siphonal tube, which is occasionally exserted, but at the 

 longer end. I have hunted out my sketches of the 

 animal, which after some search I have found in an old 

 memorandum-book of 1838, and herewith send you a 



