EXPLORATION OF ALASKA. 237 
The spermatoduct as usual, also the penis.' The spermatotheca and 
the spermatocysta as usual. The mucous gland very small, whitish 
and yellow. 
ACANTHODORIS, Gray. 
Acanthodoris, Gray, Figs. of Moll. Animals, iv, 1850, p. 108, Guide Moll. 
Brit. Mus. 1857, p. 207. . 
Acanthodoris, Alder and Hancock, Mon. Brit. Nud. Moll., vii, 1855, p. 43, 
app. p. xvii. G. O. Sars, Moll. reg. arct. Norvegiz, 1878, p. 308, 
Tab. xiy, fig. 4, ; 
Acanthodoris, R. Bergh, Gattung. Nord. Doriden, 1. c., 1879, p. 356-360. 
Forma corporis subdepressa. Nothwum supra sat grosse villosum. 
Branechia (non retractilis) e foliis tripinnatis non multis et in orbem 
positis formata. 
Caput latum, veliforme ; tentaculis brevibus, lobiformibus. Margo 
apertureum rhinophorialium lobatus. 
Discus labialis armatura e hamulis minutis formata et infra cuticula 
incrassata prominenti instructus. Lingua rhachide nuda; pleuris an- 
gustis dente laterali, hamiformi permagno et dentibus externis minutis 
(4-8). 
Ingluvies buccalis bulbo pharyngeo connata. 
Penis armatura e hamulis minutis formata instructus. Vagina 
longissima. 
The genus Acanthodoris was established by Gray, to receive the 
Doris pilosa with its non-retractile gill. Alder and Hancock adopted 
the genus, made an anatomical examination of the typical form and 
gave it natural characters, which were then adopted by Gray. In 
several new malacological publications of a systematic nature the genus 
has been omitted, and in the last twenty years no new information has 
been published, until G. O. Sars lately gave some notes on the bulbus 
pharyngeus. 
The Acanthodoridés approach the Lamellidorides, yet differ ex- 
ternally in the scattered soft villosities of the back and in the smaller 
number of the leaves of the gill, which are arranged in a circle. 
Internally they differ still more, in the presence of a strong, oral 
armature, in a different dentition (4+8+1+0+1+8+4), by a pecu- 
1 Sars (1. c. p. 16) mentions and figures (fig. 8) the penis as ‘“‘a large, 
white, conical’’ organ. : 
