382 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 23, 



in making it the type of a new genus, Mesodoti, to which must be 

 added Gyrodus gibhosus, Miinster, and Pycnodus liassicus, described 

 by myself in the 8th Decade of the ^ Memoirs of the Geological 

 Survey,' plate x. On comparing the Scotch specimen with the 

 other species of Gyrodus of which the characters of the scales are 

 known, I find it differs from them all ; I have therefore ventured 

 to give it a specific name, although it is impossible to afiirm it to be 

 a new species until more is known of the many species of the genus 

 which have been named from the teeth alone. The scales in this 

 specimen are very large, and have a dense lustrous surface of 

 ganoine. Some of these, on the flanks, measure above an inch in 

 length, including the processes. The lateral line traverses the 

 several series of scales below the column ; the scales above this line 

 decrease in size to the dorsal ridge-scales, while below it they in- 

 crease nearly to the ventral border. The scales in the hinder part 

 of the body are considerably smaller than those in front ; but they 

 retain the characteristic surface-ornament throughout. This consists 

 of an elaborate pattern in relief, composed of vermicular fillets in- 

 terspersed with granules, which covers the whole exposed portion 

 of the scales. At the two extremities of the trunk the granules 

 preponderate over the labyrinthic pattern. The nearest approach 

 to this scale-armature is found in a gigantic specimen from Solen- 

 hofen, . in the Munich Museum, called Gyrodus rhomboidalis ; but 

 there are strongly marked differences between this and the Scotch 

 species. 



Eig. 1. — Tooth of Gyrodus Fig. 2. — Scale of Gyrodus 



Goweri. Goweri. 



Mr. Joass is unable to point out the particular bed from which 

 this specimen is derived, but he says it was apparently beneath th e 

 siliceous sandstone of Braambury Hill, and decidedly above the cal- 

 careous grits, clays, and shales of Dunrobin. Oh referring to Sir 

 Eoderick Murchison's paper on the " Coalfield of Brora " *, I find 

 the beds exposed on the coast between Culgower and Portgower 

 are considered to belong to the middle portion of the Oolitic series, 



* Trans. Geol. Soc. 2ud series, vol. ii. pi. xxxi. 



