1835.] Dr. Hihhert on a Fresh Water Formation^ ^c, 69 



be distinctly traced running into the greywacke in the immediate 

 neighbourhood of Longformacus, and therefore strengthens the idea 

 of the great age of this limestone.* Besides this fern there are 

 Sphenopteris bifida^ Sphenopteris linearis, Lepidodendron sela- 

 gtnoides, L. Obovaium, L, Steinbergii, Lepidophijllum inter- 

 medium, Cyperites bicarinata, Lepidostrobus variabilis, L. 

 ornatus, Cardiacarpon acutum, Sti^maria ficoides, together 

 with species of Sigillaria, Equisetum, Calamites, and Cyclopteris, 

 which it is to be regretted had not been referred to some fossil 

 botanist, previous to the publication of this memoir. 



3. The microscopic animals found in the Burdiehouse lime- 

 stone, possess a structure in common with that of well know EntomoS' 

 traca. These are the Cypris faba, a new species which Dr. 

 Hibbert has termed Cypris Scoto Burdigalemis, and two others, 

 one of which he refers to a new genus Daphnoidea, and the remain- 

 ing to Planorbis, or perhaps a new genus. 



The shells of this description occur in very great abundance, 

 proving the extent to which this primeval lake had been supplied 

 with animal life, and the gradual and quiet nature of the calcareous 

 deposit. 



4. Fossil Fish. — The discoveries made among this class of fossils, 

 develope some of the most important facts which have been brought 

 to light of late years, not only in geology but likewise in comparative 

 anatomy, and to M. Agassiz, Professor of Natural History at Neu- 

 chatel, the credit is entirely due. 



Those fish which have been examined are referable to two orders 

 in the system of Agassiz. 



1. The Placoidean order distinguished by the irregularity in the 

 solid parts of their integuments, which consist of materials of enamel 

 often considerable or reduced to little points. The fish discovered at 

 Burdiehouse belonging to this order has been termed by Agassiz 

 Gyracanthus formosus, which approaches the modern Cestracion. 



2. The Ganoidian order distinguished by its enamelled angular 

 scales, includes the Palceoniscus Robisoni, Amblyptems, and a 

 new fish termed Eurynotus crenatus. The family of Lepedoids, 

 which is characterized by having teeth disposed like a brush in several 

 rows, or one single row of small obtuse teeth, and the Pygopterus 

 Bucklandi among the family of sauroids. But the most extraordi- 

 nary fish belonging to this family is that termed by Agassiz the 

 Megalichthys Hibberti, approaching to the Lepidosteus gavial, so 

 called from its resemblance to the crocodile of the Ganges, yet con- 

 stituting the type of a new genus. It is characterized by the alter- 

 nation of large and small teeth, which have less plicse at their base 

 with a smooth surface. The scales exhibit a coating of enamel of a 

 nut brown colour, with frequently a brilliant lustre, an angular 

 shape, and a punctured surface resembling that of the crocodile. 

 Chemical analysis of the scales confirms the supposed analogy be- 

 tween the recent Lepedosteus and Megalichthy. M. Agassiz did 

 not content himself with an -examination merely of the Burdiehouse 



* Masaz. of Nat. Hist. v. 644. 



