330 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



ANATOMICAL NOTES ON MEDYLA INSGULPTA (Pfr.). 

 By Heney Stjtek. 



Read 9th June, 1899. 



Through the kindness of Mr. Laing-, of Christcliurch, New Zealand, 

 who spent several months on Norfolk Island, I obtained a number of 

 land-shells preserved in formalin, all, with one exception, being 



Medyla (Euplecta) insculpta (Pfeiffer). 

 Selix insculpta, Pf eiffer : Proc. Zool. Soc, 1845, p, 129. 



A number of the shells contained the animal, though not in a very- 

 good condition for dissection. However, I was able to examine the 

 dentition and the genital organs, of which I propose to give a short 

 account. 



Animal. — "With two short, broad shell lobes, the left divided into 

 two ; the foot (Fig. I) shows distinct diagonal and double parapodial 

 grooves ; there is a pronounced caudal pore, situated above the 

 termination of the parapodial pore. The sole is tripartite. 



Jaiv (Fig. II). — Extremely thin and fragile, transparent, with 

 a strong median projection on the cutting edge, the outline being 

 repeated (as a remnant of an earlier stage of growth) a little higher up. 



Radula (Fig. III). — Formula 35-7-1-7-35. The minute outer 

 marginals have an aculeate mesodont, denticulated on its posterior 

 edge, with a small base of attachment ; on the succeeding inner teeth 

 the denticles, numbering from three to four, become successively more 

 and more distinct, whilst just a little below the point of the mesodont 

 an ectodont appears, consisting of two cu.sps, which are at first 

 separate, but subsequently are united at the base. The marginals 

 next gradually assume a triangular shape, and the denticles on the 

 mesodont disappear, whilst the ectodont becomes simple and larger. 

 A few transitional teeth lead to the asymmetrical laterals, each with 

 a short and stout mesocone, extending to the posterior edge of the 

 base, and a rather stout ectodont. The central tooth is tricuspid, the 

 side cusps well developed, and the mesodont of the same length as on 

 the laterals. 



Genitalia (Fig. IV). — Simple, the lower portion consisting of 

 a large, muscular, subcylindrical penis sac with a retractor muscle 

 at its posterior end, where also the vas-deferens enters. At the 

 anterior portion of the penis sac, near the atrium, an appendix is 

 inserted which has nearly half the length of the former, and is 

 slightly distended distally. The vagina is formed by a rather large 

 muscular pouch, provided with a tubular receptaculum seminis on the 

 side towards the common orifice, it is slightly bent, and does not widen 



