ANIMALS. 59 
deposits have been searched for these interesting organic remains, and even these 
rocks are doubtlessly not yet exhausted of the many varieties of Ostracoda and their 
allies, which lived and died in the shallows and depths of the ancient waters. The 
Upper Silurian Limestones, with their accompanying layers of calcareous grit, the 
Lias, locally rich in these and other Microzoa, and the Oolites, frequently swarming 
with Ostracoda, are yet unsearched. 
The various strata of the Tertiary, Cretaceous, Wealden, and Carboniferous 
formations, have been partially worked over, and the result of an examination of two 
deposits of the Permian system is now before us. To this we will now turn, 
confident that further researches in the calcareous and argillaceous deposits of nearly 
all geological epochs will discover stores of Entomostraca, if not so overflowing as in 
some of the strata of the Gault, the Wealden, the Upper Oolite, and the Magnesian 
Limestone, yet enough to reward earnest search with many additional and in- 
structive forms. 
We must, however, premise that there have been several species of Ostracodous 
Crustacea described as occurring in the older secondary rocks. M. Hisinger has figured 
and described two species from the Silurian rocks of Sweden ;' Count Miinster has given 
short descriptions of eight species from the Bergkalk of Regnitzlosan, near Hof ;* 
Prof. M‘Coy has figured and described twenty-two species from the Carboniferous 
Limestone of Ireland;’ Dr. de Koninck six species from the Carboniferous System of 
Belgium ;* and Mr. Bean one species from the Newcastle Coal-beds.’ Two fresh- 
water species are figured and described in Portlock’s ‘ Geol. Rep. of Londonderry ;” one 
in Murchison’s ‘ Sil. Syst. ;’ and others by Dr. Hibbert*® and Mr. Horner.’ Some of 
these species having been noticed by two or more authors, there remain about thirty- 
seven distinct forms belonging to the Silurian and Carboniferous rocks. One species 
of Cythere, C. Balthica, Hisinger, which occurs in the Transition-limestone of Sweden, 
appears to have been found in the Permian formation of Russia.” 
Of the ten species obtained from the Magnesian Limestone of North Britain, six are 
new; and of the others, three occur in the Carboniferous Limestone of Ireland, and 
one in the Bergkalk of Regnitzlosan. 
1 Trans. Acad. Sc. Stockholm, vol. ii, 1826. Letheea Suec., 1837, p. 9, tab. i, figs. 1 and 2; and 
tab. xxx, fig. 1. 
2 Jahrb. f. Min., &., 1830, p. 65. 
3 Journal Geol. Soc. Dublin, vol. ii, tab. v. Syn. Char. Carb. Limestone Foss. Ireland, 1844, pp. 164-68,. 
pl. xxi. 
* Descript. Anim. foss. terr. Carb. Belg., 1842, pp. 584 et seq., pl. li. 
5 Mag. Nat. Hist., vol. ix, p. 377. 
6 Page 316, pl. xxiv, fig. 13 4, ¢. 
7 Vol. i, p. 84, fig. A. 
5 Trans. Roy. Soc. Edin., vol. xiii, p. 179. 
9 Edin. New Philos. Journal, April 1836. 
10 Also in the Devonian and Silurian rocks of Russia. See Murchison, Geol. Russ. vol. ii, p. 394. 
