258 



TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Helix spatiosa, M. & H. (Macrocyclis), Proc., Acad. Nat. &ci., Philad., 1861, 



446. 



Helix vitrina, M. & H. (Macrocyclis), Proc. Acad. Nat. Sci., Philad., 1861, 447. 

 Helix Ncbrascensis, M. & H. (Macrocyclis), Proc. Acad. Nat. Sci., Philad., 1861, 



431. = H. occidentalis, M. & H. 1. c. 1857, 135 (non RECLUZ, 1845). 

 Helix vetusta (nom. trans, ob. H. v. MOR. & DR., 1857, J. C. (2), II. 153), M. & 

 H., Proc. Acad. Nat. Sci., Philad., 1860, 431 = H. vitrinoides, M. & H., 1. c., 

 1857, 135 (non DESHAYES, 1830). 

 Helix Evansi, M. & H., 1. c., 1860, 175. 

 Helix olliqua, M. & H., 1. c., 1857, 134. 



Helix strangulate/,, ADAMS. See CONRAD, Proc. Acad. Nat. Sci., Philad., 1877, 273. 

 In adopting as generic the groups formerly considered as subgeneric only, 

 the synonymy of the species is in many cases affected. Thus the name 

 diodonta, preoccupied in Helix, has precedence as a Mesodon. I have, however, 

 thought it best to retain the well-established specific name in all cases, to avoid 

 future confusion. 



The external generic characters of the animal of the various groups now 

 recognized as genera do not differ. I refer therefore for them to Patitla, the 

 first genus of dismembered Helix included in this work. 



Fig. 149. 



STROBILA, MORSE. 1 



Animal as in Patula. 



Shell umbilicated, globose conic or depressed, obliquely and coarsely striated, 

 smoother below ; whorls 5 or 6, the last globose ; aperture Innately rounded ; 

 peristome thickened, reflected ; the parietal wall and base 

 of the last whorl each with two or more entering revolv- 

 ing laminae. 



An American genus ; one of its species, however, is also 

 found in Jamaica. 



Jaw low, wide, slightly arcuate, ends scarcely attenu- 

 ated, blunt; cutting margin without median projection; 

 anterior surface with (over twelve in labyrinthica, numer- 



Animal of 5. labyrinthica ous j n Hubbardi) crowded ribs, denticulating either mar- 

 (Morse). . 



gin, and more developed on the centre 01 the jaw. 



Lingual membrane of labyrinthica as usual in Helicea, long and narrow, with 

 78 rows of 13 1 13 teeth each, with 5 per- 

 fect laterals. Morse figures 6 laterals. Cen- 

 trals with a base of attachment about square, 

 upper edge broadly reflected ; reflection very 

 short, bearing a long, slender, median cusp 

 reaching the lower edge of the base of attach- 

 ment, with a short cutting point extending 

 slightly beyond it; side cusps very small, each bearing a short cutting point. 



Fig. 150. 



Jaw of S. labyrinthica. 



Journal Portland Society Nat. Hist., I. 26 (1864). 



