TETHYS. 65 



bb. Genital opening under the hind part of the gill ; shell 

 mainly calcareous, with deeply cut, curved posterior sin us, 

 and subspiral, calloused spire; radula without central 

 tooth, the teeth all narrow, of the same form, and with 

 long, simple cusps, Dolabellince. VII. DOLABELLA. 



Subfamily APLYSIIN^E Pilsbry. 



Pleuropodial lobes well-developed, their anterior ends separated ; 

 genital orifice in front of the gill ; radula with wide, denticulate 

 rhachidian teeth, and narrower, serrate and denticulate laterals. 

 Shell flexible. 



Genus TETHYS Linne*, 1758. 



Tethys LINN., Syst. Nat. (10), p. 653, types limacina (unidentify- 

 able) and leporina (1758). PILSBRY, Proc. Acad. Nat. Sci. Phila., 

 1895, p. 347. NOT Tethys Linn., 1767, nor Tethys, Tethis, Thethys, 

 Thetis, etc., of subsequent authors, to the present day. Aplysia 

 LINN., Syst. Nat. (12), p. 1072, and of most subsequent and all mod- 

 ern authors. Laplysia LINN., torn, cit., p. 1082, type depilans. 

 Siphonotus A. ADAMS & REEVE, Zool. Samarang, Moll., p. 64 (1848), 

 type jS. geographicus (preoccupied). Syphonota PEASE, P. Z. S., 

 1860, p. ZS.Syphonopyge BRONN, Klassen und Ordnungen des 

 Thier-Reichs, iii, Malacozoa, pt. 2, p. 799 (1866), type S. geographi- 

 cus. Neaplysia COOPER, Proc. Cal. Acad. Sci., iii, p. 57 (1863), 

 A. ealifornica Coop. Esmia LEACH, Synopsis Moll. Gt. Brit, p. 33 

 (1852), type E. grlffitlisiana = young Tethys punctata Cuv. Lernea 

 BOHADSCH, 1761, (not binomial), and of Linnaeus' 5th and 6th 

 editions. Dolabella Risso, 1826, and in part of LAMARCK, 1822. 



Animal swollen behind, narrower in front, with rather lon^ neck 

 and head, bearing folded tentacles and slit rhinophores as usual in 

 the family, the latter about midway between tentacles and dorsal 

 slit. Pleuropodia arising in front of the middle of animal's length, 

 ample, freely mobile, free throughout their length or united for a 

 distance behind, functional as swimming lobes; anterior ends sep- 

 arated. Mantle nearly covering the gill, having a median tube, 

 foramen or orifice communicating with shell-cavity, and produced 

 behind in a more or less developed lobe or lobes, folded to form an 

 excurrent siphon. Genital orifice under front edge of mantle, in 

 front of gill ; opaline gland present, a short distance behind genital 

 opening. Foot well-developed. 

 5 



