MLSBRY : ON METOSTRACON, N.GEN. 27 



Metostracon mima, n.sp. PI. Ill, Figs. 1-11. 



Slug (as contracted in formaldehyde) about 40 mm. long, the sole 

 about 6 mm. wide in the middle, mantle 20 mm. long, shell 13-3 mm. 

 long. General colour smoky-grey, paler anteriorly, sparsely blotched 

 with black, and with an irregular black dorsal stripe ; mantle grey, 

 mottled and clouded with black ; sole smoky slate coloured. (See 

 PI. Ill, Figs. 1, 6, specimen from Uruapam.) 



Another specimen, the type (PI. Ill, Figs. 2-5, 7-11), from 

 Morelia, is about 30 mm. long, sole 6 mm. wide in the middle, 

 mantle 16 mm., shell ovate, 11 mm. long Sole smoky - brown, 

 colouring otherwise as described above. 



Shell ovate or oblong, slightly convex, straw-coloured and sharply 

 wrinkled in harmony with growth-lines, becoming smooth and white 

 at the rather clumsy apex, across which an adnate calcareous layer 

 is reflexed, somewhat as in Aplysia (auct. non Pilsbry). Interior 

 white and lustreless ; the columella represented by a small raised 

 ledge across the very small apical cavity. 



Length 13*3, breadth 7-8, convexity 1-3 mm. (Uruapam). 

 ,, 11, ,, 7"7, ,, 1-5 mm. (Morelia). 



Hah. — Morelia, State of Michoacan, Mexico (type locality), and 

 tJruapam, in the same State. Collected by Mr. S. IN. Ehoads. 



The two specimens differ somewhat in the shape of the shell, but 

 I do not think this indicative of specific distinction. The larger one, 

 from Uruapam, has the penis exserted. It has not been dissected. 



Anatomy of Xantuonyx. PI. Ill, Figs. 12-15. 



External Features. — Snail vitrinoid, with submedian mantle and 

 spiral semi- globular shell, and long, slender tail, with a more or less 

 pronounced terminal horn. Sole undivided. Lateral margins of foot 

 without pedal grooves, or foot-margin. Surface irregularly reticulate. 

 Mantle with a divided body-lobe on the right side, and very shortly 

 reflexed at the margins over the shell (or with well-developed shell- 

 lobes, according to Stiebel and Pfeffer). Genital aperture near the 

 right tentacle. 



Shell largely exposed, spiral, etc. 



Internal Anatomy. — Jaw flatly ribbed. 



Radula helicine. 



Genitalia. — Atrium very short. Penis short, swollen, its lumen 

 containing a large papilla at the apex ; the short epiphallus somewhat 

 narrower, continued beyond the vas-deferens in a stout flagcllum. 

 lie tractor of the penis inserted on the epiphallus at its junction with 

 the penis. The small dart-sac is inserted on the atrium, and is adnate 

 to the vagina towards the base. Where it joins the vagina, on each 

 side, the slender ducts of two large, oblong mucous glands are 

 inserted. The vagina is short and wide. The spermatheca small 

 and ovate, on an extremely long duct. The ovotestis consists of 

 several groups of short caeca, imbedded in the liver, in the apical 

 whurls of the shell. 



