74 Professor T. Rupert. Jones — Cretaceous Entomostraca. 



VII. — Notes on the Cretaceous Entomostraca. 

 By Prof. T. Exjfert Jones, F.G.S., of the Eoyal Military College, Sandhurst. 



I HAVE lately been urged to revise the Cretaceous species of 

 Entomostraca, enumerated in my Monograph, published by the 

 Palgeontogi'aphical Society in 1849. This I ought to have done ten 

 years ago, after the publication of memoirs on the Cretaceous 

 Entomostraca of Germany, the Netherlands, etc., by Eeuss, Bosquet, 

 and others, v^^herein some of my determinations of sj^ecies are cor- 

 rected from actual comparison of specimens. An improved classi- 

 fication V7as attempted in my Monogr. Tert. Entom., 1856 ; but 

 a total revision is still more necessary now, because the late 

 researches by Sars and Gr. S. Brady, in the structure and character 

 of the recent Entomostraca, have multiplied and elucidated species 

 and genera of these little bivalved Crustacea to an amazing extent. 

 So clearly has Mr. Brady's " Monograph of the recent British 

 Ostracoda" (Linnean Soc. Trans., 1868), in particular, defined the 

 several groups, that we may in very many cases form a safe opinion 

 of alliances from the shape, hinge, and other characters of the 

 carapace-valve, at least far more satisfactorily than when in 1849 

 (Monogr. Cret. Entom.), and in 1856 (Monogr. Tert. Entom.), I 

 laboured to institute some definite distinctions for fossil Entomostraca, 

 founded on these characters. 



The interchange of specimens above alluded to has cleared away 

 some obscurities ; but others remain, and I hope to go over all my 

 old work some day, with the new lights, and to reproduce the 

 necessary figures for illustration of our Cretaceous species, on a 

 smaller scale, and with much clearer and more accurate drawing 

 than we find in my Monograph of 1849. For the present, I offer 

 the subjoined remarks on the published British species. 



1. CytJiere Hilseana (Eoemer). Monogr., p. 10. M. Bosquet, having 

 compared some specimens, found that this is not Eoemer's C. 

 Hilseana, and named it C. Jonesiana in his Descript. Ent. foss. tert., 

 p. 38 (1852), and in his Crust, foss. Limbourg, p. 74 (1854). In 

 my Monogr. Tert. Entom., p. 45, however, I show that Eoemer's C. 

 perforata, Bosquet's Bairdia perforata, and the species in question 

 (which is a Cytheridea), are the same. It stands therefore as 

 Cytheridea perforata, Eoemer, sp. 



2. Cy there punctatida (Eoemer). Monogi'., p. 11. M. Bosquet has 

 shown that this is not Eoemer's C. punctatida, which, he says, is 

 probably the young of C. Hilseana (Crust, foss. Limbourg, p. 72). 

 Eeuss first named it, and it is to be registered therefore as Cythere 

 concentrica. Ess. 



3. Cythere umhonata (Williamson). Monogr., p. 12. This appears 

 to me to be probably a Oytheropteron, as defined and figured by 

 G. S. Brady in his " Monogr. recent British Entom. " and other 

 memoirs. 



4 and 5. Cythere faba (Ess.), and Cythere Bairdiana (Jones). 

 Monogr., p. 13. These appear to be rightly placed as to genus, 

 though neither is well defined ; the former, however, is not Eeuss's 



