DENTALIUM. 237 



D. ENTALIS, Linn, et Auct. 

 -D. entails, Brit. Moll. ii. p. 449, pi. 57. f. 11. 



I have only seen one live specimen of the D. entails ; the 

 organs have the same characters as those of the Tarentinum, 

 but it is very distinct; the colour is snow-white, and on 

 comparison of two shells of the same size, the D. entails will 

 be found much more slender ; the branchiae are of a paler 

 green, more scanty, thin and delicate. 



Having had good opportunities of reviewing my notes, I 

 have thought that it would be desirable to mention the result ; 

 and I am the more anxious to do so, as I have the misfortune 

 to differ on all essentials with zoologists whose talents have 

 long stamped their judgment on these subjects as authorities 

 scarcely to be disputed. I am unable to make any material 

 correction in the preceding observations ; I can only add some 

 fresh incidents and offer a few explanations. In carrying out 

 these views I must again allude to M. Deshayes' and his 

 coadjutor M. d'Orbigny's monograph ; it appears to me that 

 there are in it some misconceptions, in addition to those I have 

 already pointed out, which if passed over may mislead. 



M. Deshayes says that the convexity of the shell answers to 

 the dorsal range, and the concavity to the ventral ; the reverse 

 is the case, as I have proved in a hundred specimens, unless it 

 be contended that the foot is placed above the head or buccal 

 pouch on the dorsal range, instead of being under it on the 

 ventral line, agreeably to the order of nature. Again, the 

 heart is stated to be fixed on the dorsal surface above the 

 stomach, and in the figure delineated it is lying on that organ 

 and exceeding it in length ; but repeated examinations inform 

 me that what is called and figured as the heart is the masti- 

 catory apparatus and intestine, which He in the stomachal 

 cavity, and demonstrate their presence by a marked inflation. 

 The heart, as I have mentioned, is a minute organ at the 

 base, but separated from the stomach by a septum or rib, 

 and immersed in the centre of the dorsal and ventral surfaces ; 



