112 A Synopsis of the Recent British Ostracoda. 



Crustacea of larger type are also commonly met with, in 

 brackish waters,* e.g., Gorophium longicorne, Palcemon varians, 

 My sis vulgaris, the common shrimp, etc. ; but these, not having 

 a hard, durable, calcareous investment, are not found in the 

 fossil state. The Foraminifera which I have usually found in 

 company with the Ostracoda above mentioned are, Polystomella 

 striatopunctata, Quinqueloculina agglutinins, Trochammina in- 

 flata, Botalia Beccarii, and Nonionina depressula ; the relative 

 abundance of these forms varying with the locality.f The 

 marshes of the Northumberland and Durham coasts are the 

 only ones which have yet been carefully examined, and it is 

 quite probable that other districts might yield different species. 

 By far the greater number of Ostracoda at present known 

 have been described from fossil specimens, and the generic and 

 specific characters have, of course, been taken almost exclu- 

 sively from the external characters of the shell, the chief of 

 these being, its general form and contour, mode of hingement, 

 arrangement of lucid (or muscle) spots and style of surface 

 ornament. The general structure of the animals themselves 

 has indeed been known sufficiently to form good grounds of 

 separation between some well-defined families, such as Cypridas, 

 Cytheridse, and Cypridinidas, but the more minute anatomy 

 indicative of generic and specific differences has, until recently, 

 been very little understood or investigated. The family 

 Cytherida3, for instance, has been considered by most authors 

 as consisting of some three or four genera (or sub-genera of 

 Cy there), separated from each other by shell-characters merely, 

 and the family Cypridee of two genera. But when we consider 

 that, of the one hundred and thirty-seven species of Ostracoda 

 now known as living in the waters of Great Britain, all except 

 ten belong to these two families, and that amongst fossil 

 species the disproportion is even greater, it is evident that, 

 amongst so vast a number of species, many important diffe- 

 rences of internal structure must exist, and that these stood in 

 need only of careful investigation in order to form good 

 grounds of generic subdivision. Accordingly, we find that 

 much has of late years been done in this direction, more 

 especially by Zenker and Fischer in Germany and Kussia, and 

 by Lilljeborg and G. 0. Sars in Scandinavia. The researches 



* See my paper on " Salt Marshes and their Inhabitants," in Intellectual 

 Observed, Vol. v. p. 26. 



f Any readers of the Intellectual Observer living in the neighbourhood of 

 salt marshes or muddy estuaries would materially contribute to the knowledge of a 

 very important and interesting branch of natural history by collecting the Microzoa 

 in the manner above described. The best material for collecting-nets is " crinoline ;" 

 the things captured may be preserved, either by drying, or by immersion in dilute 

 spirit. I should myself be very glad of the opportunity of examining any such 

 collections, and would with pleasure name the specimens obtained. 



