1835.] whith occur in the Coal formation. 139 



currence in a fossil state. In the work of Desmarest on 

 fossil Crustacea, only two species are described, the Limulus 

 Walchii found in the bituminous limestone of Solenhofen 

 and Pappenheim, and the Cypris faba abounding in the 

 tertiary limestone of several places in France. To these 

 may be added another species of Cypris found in the Weal- 

 den rocks of England and figured by Mr. Mantel. They 

 appear to be more frequent in the carboniferous strata than 

 is generally suspected, as in addition to the two species 

 described in this paper, I have described and figured a 

 much more gigantic specimen (belonging to a different 

 genus) which was found near Bathgate. # The species to 

 which I have alluded was at least a foot in length, and the 

 specimen described measured nine inches, although a con- 

 siderable part of the posterior extremity was wanting. 



The animals of the family entomostraca are cheifly inhabi- 

 tants of fresh water, although several species are found in 

 saline marshes and on our shores. With the exception of 

 the Limuli they are in general extremely minute, and can 

 only be studied by the aid of the microscope. They abound 

 in every pool, and may be collected in hundreds. Many of 

 them are parasitic, and suck the juices of tadpoles and 

 fishes ; while others swim freely about. The natural his- 

 tory of these animals is very remarkable on account of the 

 numerous metamorphoses which they undergo, so that dur- 

 ing different stages of developement they have but little 

 resemblance to the mature individuals. They often change 

 their skin, and at each change can re-produce any organs 

 they may have lost, and a single fecundation suffices for 

 the females for several generations. 



If we omit the consideration of magnitude, there appears 

 to be a striking analogy between the vegetable and animal 

 inhabitants of our pools and lakes, and those of the coal 

 formation. The little equiseta seldom attaining to the 

 height of two feet, are the representatives of the ancient 

 calamites whose height exceeded 15 feet ; and the diminu- 

 tive ferns and mosses may be compared with the arborescent 

 ferns and lycopodiae of the coal, while the little entomos- 

 traca of our lakes are similar in structure, though far 



* Edinburgh Journal of Natural and Geographical Science, vol. iii. p. 352. 



