444 " THETIS " SCIENTIFIC RESULTS. 



between the end of the fully retracted proboscis and the nerve- 

 ring; further, this section issues from the proboscis, and is not 

 attached along the inturned wall of it. This section of the 

 oesophagus is not long enough to allow of any evagination, unless 

 we are to suppose that in the proboscis it is coiled as in Pyrula 

 ficus, and this, in view of the rather small diameter of the 

 proboscis, seems unlikely. What looks like the anterior end of 

 the "sac" and posterior end of the "sheath," is represented in 

 the two figures referred to. If it be supposed that the rest of 

 the sac had been cut away, the figures become explicable, and the 

 absence of that portion of the proboscis which should be attached 

 on the one hand to the inner end of sheath, and on the other to 

 the posterior end of the proboscis would be explained. 



Haller* has discussed Melongena {'■^ Pyrula^') tuba, but adds 

 nothing to our knowledge of this part of the anatomy. 



The length of the cesophagus depends on that of the proboscis, 

 and is, therefore, not, per se, of comparative value from a syste- 

 matic point of view. 



Leiblin's gland in Megalatractus is particularly large ; those of 

 Purpura lapillus and Jopas sertum, as described by Amadrut,t 

 appear to be nearly as large, whilst those of Concholepas peruvi- 

 anust and Murex trunculus^ are even larger. But from all those 

 examples it differs in being lamelliform. 



The stomach of Melongena melongena, Linn., so closely resembles 

 that of Megalatractus that the two might almost be described in the 

 same words. The following abstracts from Yanstone|| supplement 

 my own description : — " This organ is very small in proportion to 

 the size of the animal's body. . . The calibre of this organ is 

 but slightly in excess of that of the oesophagus and intestine, and 

 in this it differs from M. tuba, in which the stomach is more 

 expanded and sac-like. 



"The chief point of interest, however, is not seen until the 

 stomach is opened, and, if present in M. tuba, was overlooked by 

 Souleyet. Within the stomach of 21. inelongeiia, on the upper 

 and lower walls, there is a longitudinal series of hard cuticular 

 plates and knobs lineally disposed on a median ridge." 



In Megalatractus there are numerous narrow, longitudinal 

 lamell?e in the stomach, as well as the two rows of knobs ; these 

 are not mentioned by Vanstone as occurring in M. melongeiia, 

 nor does he show them in his fig. 4, which otherwise represents 

 the stomach of our genus. 



* Haller— Morph. Jarb., xiv., 1888, pp. 158-162. 



+ Amadrut — Loc. cit., pp. 243 and 246. 



J Haller— Loc. cit., fig. 1. 



§ Haller — Loc. cit., fig. 9. 



I, Vanstone— Linn. Soc. Journ., Zool., xxiv., 189.3, p. 370. 



