1849, it appears that the minute species of the genus Caecum, 

 from their configuration, have generally been located with the 

 Dentalia, though it will be seen that there is little concordance 

 between the animals of the two genera. I believe, with the 

 exception of M. Deshayes' monograph, that nothing has been 

 done to elucidate this curious molluscum ; and as I think that 

 eminent malacologist has mistaken the uses of some of its 

 organs, I am induced, by the facility of obtaining live speci- 

 mens of the Dentalium Tarentinum, to review and augment 

 what is at present known of it. The animal exhibits a series 

 of characters of the highest interest, in its anatomy and 

 functional developments, some of which are so anomalous, that 

 it must be considered one of the most singular of the testa- 

 ceous mollusca. 



DENTALIUM, Linnaeus. 

 D. TARENTINUM, Lamarck. 

 D. Tarentinum, Brit. Moll. ii. p. 451, pi. 5?. f. 12. 



Animal yellowish- white, conically elongated, mantle circu- 

 lar, anteriorly thick and fleshy, edge dentated, posteriorly of 

 the thinnest texture; the penultimate and antepenultimate 

 portions of its margin are bounded by two intense white mus- 

 cular elastic cordons; the united action of these has the 

 power of completely opening and closing the anterior aper- 

 ture ; when at rest, the animal, including the foot, is entirely 

 enclosed by the tougher part of the mantle which supplies the 

 place of an operculum. 



The foot is a very long and singular organ, placed in the 

 centre of the anterior end of the body, and from its position is 

 applicable for use in every direction ; it is divided into three 

 parts : the anterior one is a pointed cone acting in some 

 measure as a tentaculum, and lies in the middle portion, which 

 consists of two lateral, sinuated, symmetrical flaps or tena- 

 cula, that are usually protruded simultaneously with the 

 terminal portion, and are the parts subservient to the animal's 

 very confined locomotion,, by using the lateral appendages as 



