We may judge of their extent in certain Formations, from the fact, that in the cabinet of Count Munster, there are nearly sixty species collected from a single stratum of the Jurassic Limestone of Solenhofen. A rich harvest, therefore, remains in store for the Naturalist who will trace this interesting subject through the entire series of Geological formations.
The analogies between existing species, and certain fossil remains of Crustaceans have been beautifully illustrated by the investigations of M. Desmarest. From him we learn, that all the inequalities of the external shell in the living specie shave constant relation to distinct compartments in their internal organization. By the application of these distinctions to fossil species, he has pointed out a method of comparing them with living Crustaceans in a new and unexpected manner, and has established satisfactory analogies between the extinct and existing members of this very numerous Class, in cases where the legs and other parts on which generic distribution shave been founded, were entirely wanting.[1]
- ↑ H. Von Meyer has recently noticed five or six extinct genera of Macrourous Decapods in the Muschelkalk of Germany. (Leonhardt and Bronn Jahrbuch, 1835.)
The subject of English fossil Astacids (Crawfishes) is at this time receiving important illustration in the able hands of Pro£ Phillips.
In a recent communication to the Geological Society (June 10, 1835,) Mr. Broderip describes some very interesting remains of Crustaceans from the Lias at Lyme Regis, in the collection of Viscount Cole. In one of these, the Lamellæ of the external Antennae, the form and situation of the eyes, and other characters, show that it was a macrorous-decapod intermediate between Palinurus and the Shrimps.
A fragment of another macrourous decapod proves the existence at this early period of a crustacean approaching to Palinurus, and as large as our common Sea Crawfish.
Two other specimens exhibit the breathing organs of another delicate Crustacean, with the tips of the four larger and four smaller branchiæ preserved, and pointing towards the region of the heart, showing that these fossil Crustaceans belonged to the highest division of the Macroura.
