and Species of Nudibranchiate Mollusca. 135 



generally with corneous jaws ; odontopliore broad, with nume- 

 rous lateral spines in each transverse row. 



The genus was constituted by Ehrenberg in 1831 *, to 

 include i/.^;rte^e^/MS described by him, and Doris lacera of 

 Cuvier f. The following may also be referred to the genus : — 

 Doris marginata and D. jlammulata (?), described and figured 

 by Quoy and Gaimard J; Z). san(7i;e«ea, Rlippell §; D. sand- 

 icichensisj Souleyet ||; 11. Adamsi, Gray ^ ; and D. superba, 

 D. cardinalisj and Z). sumptuosa of Gould **. It is more 

 doubtful whether Heptabranchus Bu7-neUii^ Adams, and Doris 

 {Rhacodoris) Ko-ebsii^ Morchff, should also be included in the 

 genus. According to Adams's description and figure ||, the 

 former would seem to have all the more important characters 

 of the Hexabranchs, Avith the exception of having the bran- 

 chial bundles arranged round the anus " in a broad lunate 

 series," instead of in a circle — an appearance which may have 

 been due to the state of contraction of the specimen, and 

 which, at any rate, is not, of itself, of sufficient importance to 

 constitute a genus. M. Morch has proposed ^^ Rhacodoris'''' as a 

 subgenus of Doris, to include the Mollusca of the type D. 

 lacera, Cuvier, which he considers to have been wrongly 

 referred to Hexabranchus, Ehr. He states that in the latter 

 the branchial plumes are separately retractile in cavities as 

 well as collectively into a common branchial cavity — an idea 

 which also obtains in Adams's ' Genera &c.' In most of the 

 descriptions, including those by Cuvier, Ehrenberg, and Riip- 

 pell, the non-retractibility of the branchise is given as a cha- 

 racter. Of the twenty-nine specimens (representing five or 

 six species) in the British-Museum collection, none shows any 

 trace of retractile branchiae. Judging from the imperfect 

 description, Rhacodoris Krehsii will probably prove to be a 

 species of Doridojjsis §§. 



* ' Sjmibolse Physicse ' — Animalia evertebrata exclusis insectis. 



t Annales du Museum, vol. iv. p. 453, pi. Ixxiii. f. 1-3. 



t Voyage de 1' Astrolabe, vol. ii. pp. 255 & 257, pi. xvii. f. 1-5, 6-10. 



§ Atlas Yon E. Riippell, ' Neue wirbellose Thiere des rothen Meers,' 

 p. 28, T. viii. f. 1. 



II ' Voyage autour du Monde sur la Bonite,' Zoologie, torn. ii. p. 451, 

 pi. XXV. f. 1-4. 



iy 'Figures of Molluscous Animals,' vol. iv. p. 104, tab. 219. f. 1. 



♦* ' Otia Conchologica,' pp. 228, 229. 



tt In ' Journal de Conch yliologie,' vol. xi. p. 34. 



XX * Genera of Recent Mollusca,' vol. ii. p. 59, pi. Ixiii. f. 10. 



§§ Since the above was in type, the author has found that D. Krehsii 

 has recently been dissected and described by Bergh (in ' Journal des Mu- 

 seum Godelffroy,' Heft viii. p. 87), and shown to be a Doridopsis. 



10* 



