88 Description of New and Little known Species of 



NUDIBRANCIIIATA. 



A family of Gasteropodous Mollusca, characterized by the possession 

 of distinct, external and uncovered gills. The species of the family are 

 all marine, and with few exceptions small in size. They are sometimes, 

 with other forms of animals, called sea-slugs, arising from the fact that, 

 like land slugs, they are destitute of shells. Their body is usually 

 elongated and soft, and attached throughout its whole length to the foot, 

 or disc, upon which they crawl. They are not unfrequently covered 

 with a cloak, which in some is strengthened with calcareous spicula. The 

 head is anterior, and frequently indistinct, having one or two pairs of 

 tentacles, the upper pair of which are placed on the cloak when it is 

 present, and behind them the eyes are situated. But the characteristic 

 peculiarity of these molluscs is the appendages that constitute their 

 breathing organs, placed upon the back, always symmetrically, in plumes, 

 tufts or papillse, either forming a circle on the central line, or arranged 

 in rows upon the sides. 



None of the Nudibranchiate Mollusca appear to have been known to 

 the ancients, and even up to the time of Linnaeus they remained, with 

 one or two rare exceptions, entirely unnoticed. It was not until the 

 appearance of the celebrated " Memoires" of Cuvier, in the Annales du 

 Museum, that much attention was drawn to this subject. Since then, 

 Lamarck and Blainville contributed something to the knowledge of their 

 physiology and relations, but not much to the number of species. 



Although little had been done up to this time by British Naturalists in 

 augmenting the species of this beautiful family, they have been, since, the 

 subjects of most accurate and fruitful- research ; and the Monograph 

 now publishing by the Ray Society, on the "British Nudibranchiate Mol- 

 lusca," may be regarded as one of the most remarkable contributions made 

 to the literature of Natural History during the present century. — Conti- 

 nental naturalists have also added several new European species during 

 the last half century. 



With the imperfect knowledge of foreign species that we yet possess, 

 it is scarcely possible to arrive at any satisfactory conclusion concerning 

 the general distribution of the Nudibranchiata in the different regions of 

 the globe. The tropical forms are, as usual, larger and more brilliantly 

 coloured than those of colder climates, but the notices of extra European 

 species are so scanty, that we cannot form any idea of their numerical 

 preponderance. * * * * It cannot be doubted that a gi eat deal of the 

 apparent deficiency of other genera, in comparison with the Dorididse, in 

 foreign countries, arises from the want of proper examination, and from 

 the little attention paid by collectors to the less conspicuous forms.* 



In 1841, the celebrated Naturalist, M. Sars, announced the discovery, 

 that these little creatures undergo a metamorphosis, having on their 



* Having paid this attention to "less conspicuous forms," I am enabled to add 

 considerably to several genera. — E. F. K: 



