122 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



as in Voluta, opens into the floor of the buccal mass in front of the 

 odontophore (Fig. 6). 



The oesophagus, as in Voluta and Neptuneopsis, presents that slight 

 enlargement marking the diminution of its muscles, and then passes 

 through the nerve - collar. Behind this structure the oesophagus 

 becomes dilated and convoluted, and then receives the opening of the 

 oesophageal cascum (o.e.]; this organ differs considerably in appearance 

 from the similarly named structure in Voluta and Neptuneopsis, beiug 

 thin-walled and sacculated ; it approximates much more nearly to the 

 oesophageal caecum of Buccinum, and like that organ is of a darkish 

 colour. The stomach and intestine are like those of Voluta. The 

 circulatory, excretory, and reproductive systems call for no comment, 

 since they resemble those of the majority of the Rhachiglossa. 



The radula of Volutilithes (Fig. 7) is of special interest, for, like 

 that of Volutomitra, at present referred to the Volutida?, it exhibits 

 three teeth in each transverse row. Of these rows there are about 

 lid, but owing to the small size of the teeth the radula is small and 

 delicate. The central or rhachidian tooth is tricuspid, the three 

 cusps being subequal, and as in Voluta attached to a curved base. 

 The lateral teeth are unicuspid, each possessing an oblong base from 

 which a single cusp projects backward ; this cusp rises as high as 

 the outer cusps on the central tooth, and is situated near the inner 

 margin of the oblong base. 



In seeking for a form with which to compare the radula one 

 naturally turns in the first instance to Volutomitra, 1 the only other 

 volutoid genus with a triserial radula. At first glance this seems 

 to be a happy comparison, especially as regards the lateral teeth, 

 which have the form of flattened oblong plates from which springs 

 a very small cusp ; the central tooth of Volutomitra is, however, very 

 dissimilar to that of Volutilithes, being a simple V-shaped tooth, not 

 unlike the peculiar tooth of Amoria, a subgenus of Voluta, but which 

 is so different from that of the typical Volute, that one is inclined 

 to question the correctness of its systematic position ; at any rate, 

 it must be a very specialized form. On the whole I do not think that 

 the radula of Volutilithes has much affinity with that of Volutomitra, 

 although it is conceivable that the latter genus might have arisen 

 from the former, and in its turn have given origin to Amoria 



Professor Gwatkin has kindly looked through his large series of 

 radula? to see if any form would compare with Volutilithes, but 

 is unable to find any radula which at all suggests that of this 

 genus. He is inclined to lay stress on the side teeth, and come to 

 the conclusion that if we can compare the radula of Volutilithes with 

 that of any known form it must be with Mitra. This conclusion is 

 one which would fit in with the statements made by Fischer in his 

 Manual concerning the genus Volutomitra, which he regards as 

 a natural transition between the VolutidaB and Mitridse. Unfortunately 

 these views are not borne out by a study of the anatomy of these 



1 Troschel : " Das Gebiss der Sehnecken," Bd. ii, pi. v, fig. 56. 



