TETHYS. 65 
bb. Genital opening under the hind part of the gill; shell 
mainly calcareous, with deeply cut, curved posterior sinus, 
and subspiral, calloused spire; radula without central 
tooth, the teeth all narrow, of the same form, and with 
long, simple cusps, Dolabelline. VII. DoLaBe.ia. 
Subfamily Artysrn 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 Linné, 1758. 
Tethys Linn., Syst. Nat. (10), p. 653, types limacina (unidentify- 
able) and leporina (1758).—Pitssry, 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 
Liny., Syst. Nat. (12), p. 1072, and of most subsequent and all mod- 
ern authors.—Laplysia Linn., tom. cit., p. 1082, type depilans.— 
Siphonotus A. ADAMS & REEVE, Zool. Samarang, Moll., p. 64 (1848), 
type S. geographicus (preoccupied).—Syphonota Pease, P. Z. S., 
1860, p. 23.—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., iil, p. 57 (1863), 
A. californica Coop.—Esmia Lracu, Synopsis Moll. Gt. Brit., p.33 
(1852), type E. griffithsiana = young Tethys punctata Cuy.—Lernea 
Bouapscu, 1761, (not binomial), and of Linnzus’ 5th and 6th 
editions.—Dolabella Risso, 1826, and in part of Lamarck, 1822. 
Animal swollen behind, narrower in front, with rather long 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 
