36 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 31, 



cies of Leptolepis present the same features. It must therefore be 

 considered m reference only to degree, since in Mr. Brodie's species 

 the sculpturing on the enamelled surface is \4sible to the unassisted 

 eye, while in the other species a powerful magnifier is required to detect 

 it. The comparative thickness of the scales is perhaps a more im- 

 portant character, for this at once eliminates them from every other 

 species oi Leptolepis, and even invalidates, to a certain extent, the ge- 

 neric title. The subsequent discovery of more perfect specimens (also 

 submitted to me by Mr. Brodie) has enabled me to confirm the ge- 

 neric identity and specific differences founded on the former specimens, 

 as also to complete in detail the characters of the species. 



" The most perfect specimen shows the head and two-thirds of the 

 body, with the position of the ventral and anal fins ; another fortu- 

 nately completes the subject by exhibiting the posterior half of the 

 fish, with the dorsal, ventral and anal fins. This species is about the 

 same length as its nearest ally, Leptolepis Bi'onni, viz. between three 

 and four inches from the snout to the extremity of the tail. The 

 head, however, is proportionally smaller, being less than a fourth, 

 whereas in the former species it is more than a fourth of the entire 

 length. The other dimensions of the head are also smaller, while 

 the depth of the body immediately behind the thoracic cincture is 

 greater ; consequently the contour of the body is more regularly fusi- 

 form than in Leptolepis Bronni, or in any other species of the genus. 

 The opercular and other bones of the head are smooth and lus- 

 trous, without any tracery or ornament except the lines of growth. 

 The vertebral column is robust and composed of about thirty-six 

 vertebrse. The hsemapophyses of the six terminal bones are strong 

 and flattened for the support of the rays of the caudal fin. The pec- 

 toral fins are of mediocre size, the number of rays not being distin- 

 guishable. The ventrals are situate about midway, and are opposed 

 to the dorsal fin, which contains about a dozen rays. The caudal fin 

 is powerful and has this remarkable structure : the rays of the upper 

 lobe are principally supported by the terminal vertebrae, a few short 

 ones only being attached to the penultimate and antepenultimate apo- 

 physes ; while in the inferior lobe the rays are supported by the pro- 

 cesses of the six terminal bones of the column, which are thickened 

 and compressed to give a firmer and broader attachment for this organ. 

 This arrangement of the parts gives a somewhat heterocercal air to 

 the caudal extremity, which also obtains in other species of this genus 

 found in the lias, viz. Leptolepis Bronni, caudalis, Jilipennis, and an 

 undescribed species I have from the lias of Courcy in France. The 

 zeal of collectors and the progress of modern research have added so 

 largely to the species of many of the genera of fossil fishes, that it 

 will soon be found necessary to eliminate some of the aberrant forms 

 under new generic or subgeneric characters. Should the genus 

 Leptolepis come into this category, the form of tail above-described 

 offers an easily appreciable and appropriate feature on which to found 

 a subgeneric distinction ..." 



I have lately traced the upper lias in the south-eastern division of 



