446 " THETIS " SCIENTIFIC RESULTS. 



anterieur, que partent les vaisseaux destines a irriguer I'appareil 

 urinaire." 



(Page 255): — " L'irrigation de celui-ci [the accessory system] 

 est elle-meme tres particuliere. Du meme sinus abdominal 

 anterieur qui donne naissance aux vaisseaux du rein, part, a la 

 partie anterieure, un dernier vaisseau, qui a lui seul distribue le 

 sang a tout le second systeme renal." 



The points of difference are : — (1) That the vena-maxima, or 

 " sinus abdominal anterieur," does not serve to place in com- 

 munication the body cavity and lacun.T of the visceral coil, but 

 places the latter in communication with the rectal sinus ; (2) 

 that the nephridial branch of the vena-cephalica, or " un dernier 

 vaisseaux," etc., arises from the main trunk of the vena-cephalica, 

 and not from the vena-maxima. 



On page 246, Perrier describes in the Olividae a structure 

 resembling the ureter of M. ariianus. 



The nephridial gland apparently is of the same shape, and 

 occupies the same position in Buccinum as it does in Megcda- 

 tractus ; but Perrier's* description is a general one applied to 

 several examples, and one comes to this conclusion from a study 

 of his figures (59 and 61, to 64), as well as a perusal of his 

 description. 



The nervous systems of all the genera ranged by Bouvierf 

 under his group " Stenogiosses " are of the same concentrated 

 character as that here described. The following four systems 

 resemble that of Megalatractus. They are arranged in the order 

 of their resemblance : — 



Furjntra persica, Lamk. (Haller).| 

 Valuta ancilla, Solander (Woodward). § 

 Voluta nejjtunei, Gmelin. (Bouvier).|| 

 Fusus syracusanus, Linn. (Haller).II 



All four systems differ from that under consideration in having 

 very short cerebro-buccal commissures, and with this exception 

 the figures and descriptions of the first two of the above systems 

 apply almost perfectly to our genus. The third sj^stem differs 

 not only in the length of the cerebro-buccal commissures, but also 

 in the less degree of concrescence of cei'ebral, pleural, and pedal 

 commissures and the better differentiation of each cerebral 

 ganglion from the other. The last system, which we might have 

 expected to most closely resemble that of Megalatractus, adds to 



* Perrier — Loc. cit., p. 251. 



t Bouvier— Ann. Sei. Nat., (7), iii., 1887. 



+ Haller— Morph. Jarb., xiv., 1888, pp. 147-149, pi. v., f. 5f5 and 57. 



§ Woodward— Proc. Malae. Soc. Lond., iv., 3, 1900, pp. 117-125, pi. x. 



H Bouvier — Loc. cit., pp. 301-^06, f. 74-75. 



T Haller— Loc. dt., pp. 158-159, f. 35. 



