ON THE BRITISH NUDIBRANCHIATE MOLLUSCA. 25 



these animals alive can know how very imperfect an idea of their external 

 characters specimens preserved in spirits can convey. Considering the early 

 period at which the British naturalists of the Linnaean school applied them- 

 selves to the study of species, we are surprised to find how little was effected 

 in this department. Pennant published his 'British Zoology' in 1777, which 

 contains just three species of Nudibranchiata, under the names of Doris 

 Argo, D. verrucosa and D. electrica. The latter has not since been recog- 

 nised. No further attention appears to have been paid to these animals until 

 Colonel Montagu, to whom we are so deeply indebted for his contributions 

 to British zoology, published figures and descriptions of several species found 

 on the Devonshire coast in the Linnaean Transactions. In 1807 Dr. Turton 

 published his ' British Fauna,' where nine species were described, one only 

 of which appears to have been introduced from personal observation ; three 

 are those of Pennant and five of Montagu. The whole number of species 

 described by Montagu is twelve, published at diiFerent times between 1802 

 and 1811. For more than twenty years afterwards scarcely anything was 

 done in this department. A few species collected by Dr. Leach are pre- 

 served in the British Museum, and some additional species observed by Dr. 

 Fleming and other Scottish naturalists appeared in his ' British Animals', pub- 

 lished in 1828, at which time the number of species, including Pennant's and 

 Montagu's, only amounted to twenty. Dr. Johnston's excellent monograph 

 on the Scottish Nudibranchiata appeared in the first volume of the ' Annals of 

 Natural History' in 1838. This treatise gave a new impetus to the study of 

 the order, and with it the first adequate knowledge of the British Nudibran- 

 chiate Mollusca may be said to have commenced. An anatomical and phy- 

 siological account of the animals comprised in the order was given as far as 

 then known, and an attemjit was made to extricate the synonyms from the 

 confusion in which they had long been involved, — a task of no easy accom- 

 plishment, but necessary to remove a chief obstacle to the study of these 

 animals. This monograph, which was entirely confined to Scottish species, 

 contains descriptions of twenty-one species, ten of which were new to Bri- 

 tain. In the extensive researches that Professor Edward Forbes has made 

 among the Invertebrata of our shores, and the many new species that he has 

 added to our Fauna, the Nudibranchiata were not forgotten ; nine or ten 

 species have been added by this gentleman in different publications, and Mr. 

 Thompson of Belfast, whose success in the cultivation of Irish zoology is so 

 well known, has added at least an equal number. During the time that 

 your reporters have paid attention to the subject, it has also been their good 

 fortune to meet with many new species. Those published by them in the 

 ' Annals of Natural History,' at different times during the last three years, 

 amount to thirty-one species. 



The present number of known British species, making allowances for some 

 erroneously raised to that rank, may be stated at seventy-five, which are dis- 

 tributed in the following genera : — 



Doridce. Tritoniadce. 



Doris 18 Tritonia 3 



Goniodoris 4; Melibcea 4< 



Polycera 5 Proctonotus 1 



Thecacera 1 Eubranchus 1 



Euplocamus 1 Eolis 33 



— Pterochilus 1 



29 Calliopsea 2 



Alderia ... 1 



Total 75 46 



