TRANSACTIONS OP THE SECTIONS. 65 



He introduced to notice a Holothuria with twenty tentacula, a link which had been 

 long wanted in the history of this singular race. He described it as being not un- 

 common in deep water and rocky ground, and is sometimes a foot in length ; it is 

 called by the fishermen a "Nigger," and "Cotton Spinner," the former from its 

 dark appearance, the latter from its thread-like bunches, which it ejects, and which 

 become elongated into long and very fine tenacious threads, no doubt intended to 

 annoy any enemy which might attack them, as they adhere firmly to anything they 

 come into contact with. It is furnished with /our rows of suckers, and covered with 

 spine-like processes, and when the tentacula are withdrawn it has very much the ap- 

 pearance of a small cucumber. He minutely described the habits and peculiarities, 

 proving satisfactorily that it is new to the British fauna. 



He mentioned that Mr. Couch, Surgeon of Penzance, had found the Boar Fish in 

 abundance, and the Plain Bonito not uncommon off the Land's End ; also that a fine 

 specimen of the Maigre had been lately captured off the Cornish coast, making the 

 second within a short time. 



He produced two new calcareous corallines, Lepralia catenata and Lepralia pecti- 

 nata, which Dr. Johnston of Berwick-on-Tweed and Mr. Couch of Penzance have 

 pronounced new and good species. 



He exhibited a specimen of the Cyprcea moneta, or Money Cowry, which had been 

 trawled up off the Land's End with the animal in it. 



Mr. Peach made a short communication on the Natural History of Goran in Corn- 

 wall. 



On a New Genus of Nudibranchiate Mollusca. 

 By Professor Allman, M. R.I.J. 



Professor Allman noticed a new genus of Nudibranchiate Mollusca. The little 

 animal upon which the new genus was founded, was obtained by Professor Allman 

 in a salt-marsh on the south coast of Ireland, where it presented a singularly am- 

 phibious habit, several specimens being discovered creeping upon the leaves of Ente- 

 romorpha intestinalis and other plants quite beyond the reach of the water. The 

 peculiarities of its structure are such as to approximate it to the genus Venillia of 

 Messrs Alder and Hancock, with which it agrees in the median and dorsal termina- 

 tion of the intestine. The dorsal surface is furnished at each side with oval, rather 

 irregularly disposed branchial papillse. An examination of the moUusk in its living 

 state was unfortunately neglected, and in the specimens preserved in spirits. Professor 

 Allman, as well as Messrs Alder and Hancock, by whom they were examined, failed 

 to detect any trace of tentacula. To the new genus the name Alderia was assigned, 

 in honour of the distinguished naturalist to whom we are already so deeply indebted 

 for our knowledge of the British Nudibranchiate Mollusca. 



On a New Genus of Parasitic Arachnideans. By Professor Allman. 



On the Anatomy of Acteon viridis. By Professor Allman. 



The author controverted the assertions of M. de Quatrefages relative to numerous 

 points in the anatomy of this little moUusk, and to the position assigned to it by the 

 French naturalist in his new order Phlebenterata. Professor Allman described a di- 

 stinct heart and vascular system, and a lateral termination of the intestine, points at 

 direct variance with the statements of M. de Quatrefages. The phlebenteric sy- 

 stem of this naturalist he maintained to be nothing more than a liver, to which organ 

 it is in every respect analogous, and affords not the slightest grounds for considering 

 it a distinct system peculiar to the Gasteropods included by M. de Quatrefages in his 

 order Phlebenterata. 



The nervous system was described in detail, and shown to be of a highly developed 

 type. Seven ganglia, of which six are in pairs and one azygous, surround the oeso- 

 phagus. The organs of vision and the bodies to which Siebold attributes an auditory 

 function were described. The embryology of Acteon was traced, and it was shown 



1844^. F 



