BY C. HEDLEY. 



103 



The following anatomical notes are illustrated in the accom- 

 panying plate : — 



Hadra fraseri, Gray. — Jaw high arcuate, ends rounded, 

 crossed by about seven stout rib3 which denticulate both margins, 

 and whose breadth is equal to that of their interstices. Radula 

 possessing a rachidian tooth with a single linguiform cusp, which 

 does not surpass the posterior edge of the basal plate ; the cusps 

 of the first dozen laterals are bluntly rounded, those of the more 

 remote gradually elongate, and exhibit small denticules. 



The peculiar features presented by the genitalia are that the 

 penis sac is twice twisted back upon itself before reaching the 

 attachment of the retractor muscle, and that the attenuated genital 

 bladder at the summit of its long and slender duct offers scarcely 

 any dilatation. 



Hadra blo?nfieldi, Cox. — The genitalia of this species much 

 resemble the proceeding, the penis sac is even more contorted and 

 the genital bladder equally slight. The jaw is crossed by six wide 

 ribs, the two central being divided by a very narrow interstice. The 

 teeth are also elaborated upon a system corresponding to that of 

 fraseri ; the cusp of the central being represented by a broad almost 

 square-headed cusp in the laterals, this becomes more slender as the 

 twenty-fifth series is approached, and further on small denticules 

 appear on each side, which gradually develop until the extreme 

 marginals become symmetrically tricuspid, the central being the 

 largest projection. 



