338 Prof. T. Rupert Jones on the 



Myodocopa, including the Cypridinidee, Oouclioeciida?, and 

 the Entomoconchidse. The next allied group is the CladO- 

 COPA, represented by the Polycopid^e only. Another group 

 is the Platycopa, having the Cytherellidaj only. See Dr. 

 G. S. Brady's memoir in the Trans. Linn. Soc. vol. xxvi. 

 (1868) pp. 355 et seq., for the classification by Dr. G. 0. 

 Sars. 



The geological distribution of these and other Ostracods, 

 as well as some of the Phyllopods (as far as known), is 

 approximately shown in the Table on pp. 336 & 337. 



My purpose is now to draw attention to the most 

 noticeable of the fossil forms alluded to in the accompanying 

 Table; beginning with those from the Lower Silurian rocks, 

 and rising up through the Upper Silurian and Devonian to 

 the Carboniferous and Permian formations (in the third of 

 which Cypridinids abound), we shall have to pass by most 

 of the Mesozoic series to reach the specimens from the 

 Cretaceous and the Tertiary strata, of which we know 

 something. 



As a knowledge, however, of the recent forms is necessary, 

 the student is referred to Dr. G. S. Brady's masterly expositions 

 of the internal structure and external characters of the recent 

 species so assiduously studied by himself, G. 0. Sars, 

 C. Claus, Fr. Miiller, and others. 



1. The oldest rock in which Ci/pridina first appears in 

 unmistakable form is C. Raisinice, J., probably of Lower 

 Silurian (Ordovician) age, as far as can be determined. It 

 measures 9 by 5 millim. See Quart. Journ. Geol, Soc. 

 vol. xlix. (1893) pp. 163, 164, with a woodcut. Miss Baisin 

 discovered the fossil " in an indurated argillite," associated 

 with the volcanic rocks of Pared-llech-y-menyn, on the south 

 coast of the Lleyu promontory, North Wales. (PL XVII. 

 fig. 18.) 



" Analogous features in various degrees, and associated 

 with other characteristics, exist in Cijpridina Reynaudii, 

 Milne-Edwards, C. elongata, Brady, G. Bairdii^ Brady, 

 C.jo2Jonica, Brady, and other hooded and apiculate members 

 of the genus ; but none of these have the hinder end tapering 

 away to so long and strong a point. A Ibssil form, however, 

 from the Carboniferous series of Sicily, described and figured 

 by Prof. G. G. Gemmellaro {Fhilomedes acanthoides^ Gemm. 

 Mem. Soc. Ital. Sci. ser. 3, vol. viii. 1890, p. 37, pi. v. 

 figs. 16 and 17), is very similar, but is too attenuate, and 

 measures 6*5 by 3 millim." 



