LINGUAL DENTITION OF SOME WEST-INDIAN GASTEROPODA. 



19 



Plecocheilus 



pellucid teeth; medians 



A broad ribbon, 1 of an inch long, of subquadrate 



laterals having bases produced on both sides, and differing from medians in having similar 



central cusps, on each side of which is a nearly obsolete toothlet; the extreme oiiter 



modified in form as well as in character. 



rows 



Mandi 



Fig. 4a. Side view of central cusps. 



Fig. 5. Tornatellina lamellata, magnified 300 diameters. A narrow band, ^ of an inch in length, ol 



numerous pellucid teeth; medium small, simple, and inconspicuous, central cusps prolonged; 



laterals large and simple, with long pellucid acute central cusps, and two obsolete dentation 



on the outer side. 



Fig 5« Side view of central cusps. The mandible is horseshoe-shaped, and composed of a number of 



pentagonal prisms laid obliquely, resembling the shell-structure of Brachiopoda. This specie* 

 is viviparous, and during July and August is found full of young animals. 



deft 



Band | of an inch long. Formula 10. 1 . 10. 



Medi 



A narrow band, -^ of an inch in length, filled 



into the basement membrane. The animal is of a delicate pink or yellow colour ; it is found 

 both on trees and the ground in the forests. 

 Fig. 7. Macroceramus signal us, magnified 150 diameters. 



with divergent rows of pellucid teeth; medians simple, elongated, with simple obtuse cusps; the 



laterals have two reflexed subequal cusps. 



Fig. la. Side view of central cusps. 



Fig. 8. Cistula pupiformis, magnified 300 diameters. 00 . 2 . 1 . 2 . 00. Lingual band small and delicate ; 



medians denticulate, with acute cusps, outer cusp- prolonged; 14 laterals broad at bases, with 

 prolonged central cusps, and with subdued denticulations on either side ; 2nd laterals broad, 



recur 



Nerit 



medians 



towards their bases, subopaque ; 1*/ laterals subtrapezoidal, with outer corner most produced ; 

 2nd laterals prolonged, strongly curved outwards ; Zrd laterals convex, broad, glassy, denticu- 

 late with curved tips; uncini strong and numerous. Between the 2nd and 3rd laterals there 

 appears to be a smaller or intermediate set of finer uncini; but whether they form a portion 

 of the odontophore, and have become accidentally turned down, or really are another set, w 

 have not been able to determine ; the peculiarities, however, of the band appear to have been 

 heretofore overlooked. 



dia/is 



Fig 10. Adamsiella aripensis, magnified 300 diameters. 00.2.1.2.00. A long slender band; m 



denticulate, with acute cusps; inner laterals broad; outer denticulate on the reflexed edge; 

 uneini numerous, slender, curved at their terminations: «, separated uncini; b, inner laterals ; 

 c, outer laterals, more highly magnified. The mollusk is frequently found suspended by two 

 or three glutinous threads from under branches of low-growing shrubs. 



Fig 11 Cyclotus transit Jus, magnified 150 diameters. 3.1.3. A narrow band * an inch long; me- 

 dians subquadrate, denticulate, cusps recurved, central ones large and acute; Is/ latera, 



* 



or claw-shaped ; bright amber-colour. The animal is of a pinkish colour, which is lighter about 



the body and foot, but deeper about the tentacles. 

 Fig. 11«. Mandible of Cychtu*, magnified 150 diameters. It is divided into two portions by a median 



articulation, and covered with fine acute denticulations in divergent row^. 

 Pig 12 Cylindrella trim tan a, magnified 200 diameters. Formula 2.1.2. A narrow band T \ of an 



inch in length; medians well developed, acute, tricuspid, tubercles on their bases; 1st laterals 



