446 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. V. 



OSMEROIDES. Wall-case D. 1 (No. 26). The fossil fishes of the Salmon 

 family, from the Sussex chalk, deposited in this Case, were the most 

 beautiful ichthyolites in my collection ; and though since the exposure 

 of the specimens to the atmosphere of London they have lost much of 

 their original brightness, and the pure white chalk appears like chalk- 

 marl, yet the uncompressed state of many of these fishes, and the high 

 relief in which they appear, render them objects of interest even to the 

 uninstructed observer. These Ichthyolites are nearly related to the 

 common Smelt (Osmerus) ; whence the name given to the genus, Osme- 

 roides, by M. Agassiz. They were discovered, figured, and described, in 

 my " Fossils of the South Downs," under the name of Salmo Lewesiensis. 

 There are three species, two of which are well marked, viz. 0. Mantelli, 

 and 0. Lewesiensis. The former has a short subcylindrical body, and 

 seldom exceeds nine inches in length ; the latter is of an elongated form, 

 and sometimes attains a length of fourteen inches ; the dorsal fin has 

 more rays than in the former. 



The first species is generally found with the head and body uncom- 

 pressed ; the most remarkable specimen hitherto discovered is on the 

 front ledge of No. 26, and is figured in Lign. 92. This matchless 

 ichthyolite is nine inches long, and the chalk has been cleared away so 

 as to expose the entire body, lying six inches in relief above the block, 

 to which it is attached by the dorsal aspect. The mouth of the fish is 

 open, the opercula or gill-covers, and the branchial arches are expanded ; 

 the pectoral and ventral fins, and the dorsal fin, are in their natural 

 position ; the five rays of the dorsal are erect : there are but few traces 

 of the caudal fin ; in a specimen of Osmeroides Lewesiensis, in the same 

 Case, a little adipose process, as in the recent Salmons, is situated 

 between the dorsal fin and the tail. 2 



ACROGNATHUS (A. boops). W all-case D. (No. 25.) This is a small 

 unique ichthyolite which I discovered in a block of chalk from Souther- 

 ham. It is an abdominal cycloid fish, with a large and flat head, and 

 enormous orbits. The form of the fish, when recent, is shown in 

 Lign. 93. 



AULOLEPIS (A. typus). Near the last described fossil there is placed 

 another unique fish from the same locality, which is characterised by its 

 slender muzzle, and conical teeth. The figure of the original is given in 

 Lign. 94. 



ICHTHTOLITES OP RECENT SPECIES J MALLOTUS. Wall-case D. (No. 27.) 



The eminent naturalist to whose labours the Ichthyologist is so greatly 



Medals of Creation," pp. 594, 604. 



