106 PROCEEDINGS OF THE ACADEMY OF [1880. 



Limbus frontalis digitatus vel tuberculatus. Branchia S-Y-foliata. 

 Appendices dorsales (extrabranchiales) 1-3. Tentacula brevia, lobi- 

 formia. 



Lamelhe mandibulares laterales forte?, sat applanataj. Radula 

 rhachide nuda ; pleuris dentibus lateralibus hamatis duobus (margine 

 Isevi), interne minore, externo majore, et dentibus externus 4-8. 



Prostata magna ; pleuris ut in omnibus Polyceratis. 



The genus Polycera was established by Cuvier (1812 ?), to receive 

 the Doris quadrilineata of Miiller and (in 1830) allied forms ; a few 

 years afterwards (1815), and not knowing the genus of Cuvier, Oken 

 formed his Themisto, nearly identical with the Polycera of Cuvier.* 

 The Gufeea of Leach (1852), is entirety congeneric with the genera 

 of Cuvier and Oken, as is also very likely the Phanerobranchus of 

 A. Fredol (Moquin-Tandon). The Limacia of 0. Fr. Muller (1781), 

 contains a whole series of different Nudibranchiata, among them the 

 D. quadrilineata, and, as first-named species, the D. verrucosa; the 

 name cannot therefore be employed here. 



Although, tlirough Cuvier and Alder (1841), their external char- 

 acters were somewhat made known, still Polycera, like so many 

 other Nudibranchiata, remained very superficially known, until the 

 laro-e monograph of Alder and Hancock, ^ that first really unveiled 

 their external and internal structure, although Frey and Leuckarf'' 

 had given some anatomical notices of these animals. Lately more 

 light has been spread over the northern species of the group, through 

 the investigations of Meyer and Moebius,^ and of G. O. Sars.* 



The true Polycera shows a form of body common to the whole 

 family. The well-developed frontal margin is more or less curved in 



* A careful search has failed to find any other ground for supposing that 

 Cuvier described the genus Polycera in 1812, or at any date before 1817, so 

 that the 1812 of Hermaunsen is almost certainly merely a misprint. The 

 name Themisto, of Oken, if congeneric, should therefore take precedence. 

 — Dall. 



1 Alder and Hancock, Monogr. Brit. Nudibr. Moll., Part 2, 1846, fam. 1, 

 PI. 23 ; Part 4, 1848, fam. 1, PI. 24 ; Part 5, 1851, fam. 1, PI. 22 ; Part 6, 

 1854, fam. 1, PI. 17 (anat. !) ; Part 7, 1855, PI. 46 supplem. figs. 20, 21. 



'^ Frey and Leuckart, Beitr. zur Kenntn. wirbellose Thiere, 1847, p. 66- 



70, taf. i, fig. 1§, 13. 



3 Meyer and Moebius, Fauna der Kieler Bucht, i, 1865, p. 49-57, m. 2 

 taf. uud taf. iv. A, B. 



* G. 0. Sars, Moll. reg. arct. Norv., 1878, p. 312, 813, Tab. xiv, fig. 14-16. 



