ox OSTRACODA DREDGED AMONGST THE HEBRIDES. 209 



inhabitants of other seas, and one {Ciitheropteron irlcorne) is now for the 

 first time noted as occurring in a recent state. It should, however, be men- 

 tioned that, of the fifteen species here named as new to our seas, eleven were 

 previously represented in my collection by specimens (unrecorded) from other 

 parts of the British coast. 



A sjiecies closely allied to Ihjohates pratexta (/. r/lacialis, MS.) has been 

 found by Messrs. Crosskey and Robertson pretty abundantly in the fossil 

 state in the oldest deposit of glacial clay which has come under their 

 notice, and it is worthy of remark that the recent species now dredged is 

 much smaller and apparently more poorly developed than the fossil one, 

 though in general character and appearance so much like it as to make me 

 suspect that the one may possibly be the lineal descendant of the other. If 

 this be so, it forms an interesting contrast to C'>/theridea jp^'P'^^osa, the 

 living specimens of which are mostly much finer than those of the tertiary 

 period. C. ixtpRlosa is an abundant species in many districts — in Loch Fyne, 

 for instance, it occurs in immense numbers and of fine growth — while Ihj- 

 ohates prcetexta appears to be rare, and is probably confined to our uorthern 

 seas. We may therefore infer that the one species is verging towards ex- 

 tinction, at least in our latitudes, while the other is thriving, and for the jire- 

 sent successful in the " struggle for existence.'' Of the sixty species here 

 catalogued, thirty-two are known to occur in the glacial clays of Scotland ; 

 these are marked with an asterisk, and it may be noted that the two sjiecies 

 which perhaps occur most abundantly in the older clays, Cytlieridea punc- 

 tillata and CyOiere concinnci, do not appear to be of frequent occurrence at 

 the present day, and are confined to northern habitats. 



As to the geographical distribution of the various species, it may be re- 

 marked that sixteen of the number are essentially northern in their range, so 

 far as our present knowledge extends ; these are Bairdia obtusata, B. compla- 

 wita, Ci/there concinna, C. angidata, C. Dmielmensis, Cytlieridea papUlosa, 

 C punctillata, C inermis, C. dentata, Ilyohates prcetex'ta, BytJiocythere sim- 

 plex, B. jlexuosa, Pseudocy there caudata, Cytherella lavis, C. Scotica, and 

 Cypridina Mac Andrei. None of these have been found (except one or two 

 specimens of Cytlieridea punctillata) in any locality south of the Dogger 

 Bank, and most of them are confined to the shores of Scotland. On the 

 other hand, our list includes one species which attains its highest develop- 

 ment in more southern localities, such as the seas around the Channel 

 Islands, the south coast of England, and the south-west of Ireland. This is 

 Cythere emaciafa, of which only one specimen, and that a poor one, has been 

 detected in the Hebridean gatherings. 



It is impossible at present to institute any satisfactory comparison between 

 the recent Ostracoda of our seas and those of the Continent, as, except in 

 Scandinavia, scarcely anything has been done amongst this group by conti- 

 nental natiiralists. In general terms, however, it may be said that the 

 Ostracoda of the K^orthern British seas exhibit a close approach to those of 

 Norway. 



Descriptions of new Species, 



PoNTOCrPEtS ACtrPtTNCTATA, n. Sp. 



Oblong, subreniform, highest in the middle, height equal to half the 

 length. Anterior extremity rounded, posterior obtusely pointed. Dorsal 

 margin arched, sloping more steeply behind than in front, ventral mai'gin 

 deeply sinuated at the anterior third. Outline, as seen from above, com- 



1866. p 



