in Flints of the Chalk. 19? 



ber of fossil fishes belong to the two orders with enamelled 

 scales." 



It will be evident from an inspection of the plates, that the 

 scales now described, with the exception of those represented 

 at Nos. 2, 6, and 25, belonged to fishes of the last two orders, 

 or those with unenamelled scales, indicating therefore an ap- 

 proximation to existing species ; and the extraordinary simi- 

 larity in general characters between the fossil and recent 

 scales will at once be apparent from a comparison of the re- 

 spective drawings. The latter were very obligingly supplied 

 to me by Mr. Yarrell out of his private and unpublished 

 collection, and are from the pencil of Mr. Charles Curtis. 

 The former I traced under the microscope with a power of 

 about 25 linear, and they were reduced and lithographed by 

 Mr. Aldous, who is making larger drawings to preserve their 

 relative proportions. 



These scales vary in size from T %ths to ^th of an inch in 

 diameter,* and are arranged in the order of their magnitude. 

 The concentric lines, which vary with the age of the fish, are 

 the most numerous on No. 10, being nearly 100, whereas there 

 are about 14 only on No. 27. In Nos. 3. 12. 19. there are be- 

 tween 40 and 60. A recent scale in Mr. Yarrell's collection, 

 which measures 8~ inches in circumference, has upwards of 300 

 concentric circles. The fish from which this scale was taken 

 is of the genus Chatcessus, Cuv.fj and is now in the British 

 Museum. The row of scales along the sides of fishes, forming 

 the well-known lateral line, in addition to the structure com- 

 mon to the scales of the other parts of the body, are pierced 

 through near the centre by a tube which allows the escape of 

 the mucous secretion, produced by the glands beneath. Each 

 of the scales represented in Nos. 4. 12. 14. 18. exhibits this 

 tube with the numerous lines peculiar to the species. It is 

 here no doubt that we are to look for scales possessing the 

 most decided specific characters, for, as I learn fromMr. Yarrell, 

 who has gone into much detail upon this subject which he has 

 not yet made public, though scales of the same fish differ in 



* The largest scale I have as yet found is similar to No. 2, and measures 

 T fi (T ths by -rVhs f an inch. Very fine examples of coniferous wood occur also 

 in these flints. 



t Regne Animal. Edition 1829, vol. ii. p. 320. 



