286 



ANATOMICAL AND SYSTEMATIC NOTES ON BORCASIA, TRIGO- 

 NEPHRUS, N.GEN., GORILLA, TRERSITES, AND CHLORITIS. 



By Prof. Henry A. Pilsbry, Sc.D., etc. 



Read lith April, 1905. 



(PLATES XIII AND XIV.) 



I OWE to Messrs. John Ponsonby and Gr. K. Gude the opportunity of 

 dissecting a number of Helices not hitherto described anatomically. 

 Two of them, '■ Helix ^ globulus, Miiller, and Corilla Humherti, Brot, 

 represent groups of such high interest that I need not apologise for 

 discussing them at some length. 



The genera. Doroasia, Gray, and Trigonephrus, n.gen. 



Borcasia was iiistituted by J. E. Gray (1838, p. 268) for the species 

 D. Alexandri, Gray. Dr. Fleck collected a living specimen of 

 D. Alexandri some years ago, and Simroth has given a short account 

 of its anatomy (1894, p. 94). The same specimen — an immature one 

 — furnished the notes and figures given by me (1895, p. 172). From 

 these imperfect data it appears that Helix globulus differs from 

 D. Alexandri in several important particulars, so that while the two 

 are probably more nearly related to one another than either is to other 

 known genera, yet it seems necessary to erect a new generic group for 

 the species globulus and its immediate allies. The two groups will be 

 distinguished as follows : — 



Borcasia, type Alexmidri. Trigonephrus, type globulus. 



Vas deferens free throughout. Vas deferens closely bound to the penis 



and oviduct, nowhere free. 



Duct of the spermatheca long, inserted Duct of sperniatheca short, inserted on 



upon a rather long vagina. the atrium. 



Central and inner lateral teeth with AU of the teeth tricuspid. 

 mesoGones only ; outer lateral and 

 marginal teeth with the ectocone de- 

 veloped. 



Shell depressed, SheU globular. 



Anatomy of Trigonephrus globulus. 



The foot is short and broad, the tail depressed, rounded posteriorly, 

 evenly granulate. 



The jaw is solid, moderately arched, and smooth. 



The radula is large for the size of the snail, measuring about 8 mm, 

 long, 4 wide. The teeth stand in nearly straight transverse rows, 

 about 90 teeth in a row. The central and lateral teeth are so similar 

 that the middle series can be found only with difficulty. These teeth 

 (PI. XIV, Fig. 15) are tricuspid, the mesocones being about as long 

 as the basal plates, the side cusps distinctly overhanging, ectocone and 

 entocone being nearly equal. The transition to the marginal type of 



