886 American Work on Recent Mollusca in 1881. [November, 



Intimately related to the material forming the subject of the 

 foregoing papers, is that treated of in a paper " On certain Lim- 

 pets and Chitons from the the deep waters off the eastern coast 

 of the United States " (Proc. U. S. Nat. Mus, 1881, pp. 400-414), 

 by W. H. Dall. Certain very ordinary-looking little limpets from 

 deep water were kindly submitted to the author by Professor 

 Vernll, together with specimens of his Lepeiella tubicola. The 

 examination showed that these forms were of the highest inter- 

 est, and belonged to two orders, Rhiphidoglossa and Docoglossa, 

 most of the species appearing to be blind. Of the former group 

 there were three species belonging to two genera, both nearer 

 to each other than to any described genus of the order, but differ- 

 ing so much as to necessitate their separation into distinct fam- 

 ilies which are described as follows : Family Cocculinidae Dall, 

 containing the genus Cocculina Dall, with the two new species, 

 C. rathbuni and C. beanii. The dentition closely resembles that 

 of Parmophorus and Helicina, and indicates a relation of this 

 family to the following one, such as in the Pulmonata is sustained 

 . by the Cyclostomacea to the Cyclotacea as denned by TroscheL 

 The internal and external anatomy present a curious mingling of 

 features supposed to be characteristic of the Docoglossa and 

 Rhiphidoglossa. The second family, Addisoniidae Dall, includes 

 the genus Addisonia with the new species A. paradoxa. This 

 has a remarkable shell resembling Pilidium Midd. (Capu- 

 lacmaea Sars). It, or closely allied species, has been described 

 from the Mediterranean, under the name of Gadinia excen- 

 trica Tiberi, but it has no relations with Gadinia. The soft 

 parts are crowded to one side to make room for a curi- 

 ously exaggerated gill or rather series of branchial leaflets. The 

 dentition is different from anything hitherto recorded in the 

 Rhiphidoglossa, showing Docoglossal features, while the remain- 

 der of the anatomy is less like the true limpets than that of Coc- 

 culina. Among the Docoglossa the characters of Lepetella Ver- 

 rill are determined. It presents certain peculiarities and, for the 

 group, a very abnormal dentition, which have led the writer to 

 separate it in a distinct subfamily, Lepetellinae from Lepeta, etc. 

 Peciinodonta arcuata, n. g. et sp., is proposed for a curious form 

 allied to Scutellina, blind and with a dentition composed of one 

 large pectinate lateral on each side of the median line. The wri- 

 ter suggests that the peculiarities of the Docoglossal dentition 



