184 



TERRESTRIAL AIR-BREATHING MOLLUSKS. 



dart sac, with the penis, there are two short rt tractor muscles inserted. The 

 cloaca is narrow and cylindrical, and has surrounding two thirds of its middle 

 a thick glandular organ. Interiorly, the penis sac, cloaca, etc., have a longitu- 

 dinal rugose surface. 



Spurious Species of Tebennophorus, etc. 

 Tebennopkorus bilineatus, Cart., United States, of Grateloup (Dist. Geog. p. 



30), is unknown to me. 

 Philomycus quadrilus, fuscus, oryrus, and flcxuolnris of Rafinesque (see Vol. 



I. p. 51 and 52), and Philomycus (Eumelus) Hindus and nebulosus are placed 



in the same genus as Tebennophorus Carolinmsis by Gray and Pfeiffer, 



Brit. Mus. Cat. They are unknown to me. 

 Tebennophorus dorsalis : see Pallifera. 



HELICODISCUS, Morse. 

 Animal heliciform : mantle posterior, thin, simple, protected by a shell ; other 

 characters as in P alula. 



Shell discoidal, widely umbilicatcd, not shining; spire 

 concave ; whorls 4, equally visible above and below, 

 the last scarcely larger than the rest, not deflected ; 

 aperture rounded, vertical ; several pairs of tubercles 

 at intervals within, on the inner surface of the outer 

 whorl ; peristome simple, straight, its margins distant. 

 Jaw, according to Morse, of the only known spe- 

 cies, H. lineatus, low, wide, crescentic, ends much at- 



FiG . 91 tenuated, acute ; cutting margin with a median, 



beak-like projection ; anterior surface without 

 ribs, but covered with striae converging ob- 

 jaw of H. lineatus. lj que ly towards the beak -like prominence. 



Fi^. 92 shows the general arrangement of the teeth upon the lingual mem- 

 brane. The characters of the separate teeth are better shown in Plate IV. 



Fig. 92. 



Fig. 90. 



\ 



V- 



Animal of H lineatus, 

 enlarged (Morse). 



Lingual dentition of if. lineatus (Morse). 



Fi<'. M. Morse gives 77 rows of 12 — 1 — 12 teeth, each with 4 perfect laterals. 

 Leidy, in Vol. II. 262, Fig., gives 13—1—13 teeth, with 5 perfect laterals. 

 The membrane examined by me has 12—1—12 teeth, with 4 perfect laterals. 

 The central teeth have a base of attachment very small, longer than wide, with 

 expanded lower angles, and reflected upper margin. Reflection very small, 



