342 



Transactions. 



Anterior tentacles short, ommatophores distant, long, granular, 

 with very broad bases. Foot broad, narrowly rounded behind. 

 Mantle margin even, with a fold on the under surface in front 

 of the respiratory orifice. Genital orifice behind the right 

 ommatophore. 



40 



Jaw (fig. 1) arcuate, attenuated at the ends, irregularly 

 striated by infoldings of the membrane. 



Radula (fig. 2) tongue-shaped, of about 130 transverse rows 

 of teeth, which are nearly straight, forming a very obtuse angle, 

 salient posteriorly. Formula of radula : 20 . 30 . 1 . 30 . 20. 

 The central tooth elongated, with a long and broad mesodont 

 and a low and broadly rounded mesocone ; usually there are 

 two minute side-cusps present. Lateral teeth, numbering about 

 30, with a very broad rounded mesodont, the mesocone short 

 and broad ; there is no endodont, but the ectodont is distinct, 

 narrowly rounded, bearing a minute cutting-point. The mar- 

 ginals are narrower and with two cutting-points ; towards the 

 margins they are getting very narrow and indistinct, and it 

 is impossible to exactly ascertain their number. 



Reproductive Organs (fig. 3). — The male organ is very large, 

 with the retractor muscle at its apex and 

 the walls very thick. The vas deferens 

 enters near the apex, and it is free only for 

 a very short distance at the base. The 

 albumen-gland is large. The most remark- 

 able feature is the absence of a recepta- 

 culum seminis, which is present in P. 

 hongii. 



Remarks. — The teeth of the radula 

 differ somewhat from those of P. hongii : 

 in the latter the central tooth has no side 

 cusps, the transition teeth between laterals 

 and marginals are getting tricuspidate, 

 and most of the marginals show the same 

 character. There is no difference in the 

 reproductive organs of the two species 

 except the absence of the spermatheca in 

 P. hollonsi, and I found it to be absent in four specimens which I 

 dissected. 



