90 PROCEEDINGS OF THE ACADEMY OP [1880. 



little sac, which seems to be homologous with the biliary sac (pancreas, 

 autt.) of other Dorididse. Alder and Hancock, therefore, have de- 

 nominated that part of the digestive tract as " stomach," although it 

 in no essential respect differs from the rest of the intestine, and is 

 just like that part in the Chromodorides, and should be undoubtedly 

 regarded as the pyloric part of the intestine, when that sac opened 

 lower down, as in the Chromodorides,^ in the cavity, which is included 

 in the liver, and seems to be the true stomach. The spermatoduct and 

 the chief duct of the spermatotheca (vagina) are of very considerable 

 ■ length ; the former consisting of two different parts, a superior softer, 

 and an inferior very muscular part, internally clothed with an arma- 

 ture, which is continuous through the penis. This last is rather short, 

 the superior part solid and projecting as an armed glans into the in- 

 ferior, hollow part (prseputium). The armature consists of rows of 

 hooks continued in the interior of the organ, and, as mentioned above, 

 farther upwards ; quite like that of the Polyceridse^^ Fhyllidiidse^ 

 and Doriopsidae.* 



About the biological relations of these forms very little is yet known 

 and that only with reference to the typical species, through Alder and 

 Hancock, as well as Meyer and Moebius. The spawn is figured by 

 Alder and Hancock (1. c, PI. 15, fig. 9), and by Meyer and Moebius 

 (1. c, fig. 13, 14) ; about the development nothing is yet known. 



The few known species of this genus seem limited to the northern 

 parts of the Atlantic and of the Pacific. 



1. Acanthodoris pilosa (O, F. Miiller). Oceanum Atlanticum et Pacificum, 

 Doris pilosa, Cuv. 

 Doris stellata (6m.), Cuv.* 



> Cf. my Malacolog. Unters. (Semper, Philipp., II, ii), Heft xi, 1877, p. 

 464-494 ; Neue Nacktschnecken der Siidsee, 11, Journ. der Mus. Godeffroy, 

 Heft viii, 1875, p. 72-82 ; idem, iv, 1. c, Heft xiv, 1879, p. 1-21. 



2 Cf. my Malacolog. Uuters. (Semper, Philipp., II, ii), Heft xi, 1877 

 (Trevelyana. Nembrotha). 



^ Cf. my Bidr. til en Monogr. af Phyllidierne, Naturh., Tidskr. 3, R. V., 

 1869 ; Malacolog. Unters. (Semper, Philipp., II, ii), Heft x, 1876, p. 377- 

 387. 



* Cf., 1. c, Heffc X, 1876, p. 384-387 ; Journ. der Mus. Godeffroy, Heft 

 viii, 1875, p. 82 94. 



^ According to Fischer (Note sur quelques especes du G. Doris, decrites 

 par Cuvier, Journ de Conchyl. 3 ser. x, 1870, p. 290), the Doris stellata, 

 Cuv., and the D Icevis, Cuv., are identical with his D. pilosa, and this with 

 the typical form of Miiller. 



The D. stellata of Philippi seems a quite different form, a Platydoris 



