193 REPORT — 1875. 



throe years' dredgiugs of the Tyueside Naturalists' Pield-CIub, we are how 

 able to add 21 species. 



From the same dredgiugs 19 species of Ostracoda were catalogued by 

 Mr. Norman, but five years later the number was increased to 47 by 

 Mr. G. S. 13rady. Our present list includes 71 species, oue of which, 

 Ct/therideis Hilda, is new to science. 



The Eev. A. M. Norman, who accompanied us during part of the dredging- 

 oxpedition, has kindly examined and reported on the Polyzoa, Hydrozoa, and 

 iSpongozoa. Among the Polyzoa is one interesting form new to the British 

 seas, Bugida fruticosa, Packard ; one Hydrozoon new to the east coast, Lafoea 

 jiocillum, Hincks ; and two undescribed sponges, Uipneniaddon virgulatvs 

 and Hcdiclwndria virgea, both of which arc here described by Dr. Bowerbank. 



The Foraminifera from the earlier dredgings were ably worked out by 

 Mr. H. B. Brady, and numbered 70 species, a total subsequently increased to 

 74, or perhaps rather more. The list will now, with the additions wc have 

 made, comprise 94 species, or rather more than 60 per cent, of the recorded 

 British Poraminifera. 



But apart from the number of species obtained there is much of interest in 

 their distribution, as may conveniently bo seen in tlie annexed Tables. It 

 was shown by Mr. Alder* that the Testaceous Mollusca of tlie Northumber- 

 land coast present a distinctly boreal character, which is shared more or less 

 by the whole invertebrate fauna ; but it may be rcmariced with regard to the 

 Ostracoda that this character is by no means so apparent. It will be seen 

 from the Table that Cythere httea, C. viridis, C. aiujiduia, Cyfheridea pnnc- 

 tlUata, and Ci/theru7-a nigrescens are absent or rare. All these species arc 

 characteristically boreal, and strongly represented in the Posttertiary (" Gla- 

 cial") clays of Scotland. At the same time it is interesting to note that 

 although CgtJiere latca and Cgtherura nigrescens are absent or rare in the 

 dredgings from this coast, they are extremely common between tide-marks, 

 where they must be subject to- much greater variation of temperature. But 

 if a low temperature were specially congenial to these species, we should 

 expect to find them further out at sea, where they certainly lived in great 

 abundance during the deposition of our Posttertiary clays. It is a curious 

 fact that these two species are confined almost entirely to the littoral and 

 Laminarian zones of the east coast, but are abundant in deep Avater on the 

 west, as, for instance, in the Frith of Clyde. On the whole, then, we must 

 conclude that the Ostracoda and Forarainifera of the north-east coast of 

 England do not present that marked arctic character which has been noticed 

 in a considerable group of the Northumbrian Mollusca ; but that there is, on 

 the contrary, a marked absence of some typically northern forms which are 

 abundant in the M'armer seas of the western coast. Nor can we suppose that 

 a cold arctic current is the only or even perhaps the chief agent in the con- 

 tinued existence of this peculiar Northumbrian moUuscan fauna, else we 

 could scarcely fail to have had an equally well-marked development of arctic 

 types amongst other groups of invertebrata whoso organization renders them 

 even more easy of distribution. We must therefore, in the absence of more 

 accurate information, look to some strictly local circumstances as having been 

 the chief causes of the retention of the species in question over particular 

 circumscribed areas. 



* Natural-History Transactions of Northumberland and Durham, 1865. 



