Reviews — Dr. B. Dean — Pineal Foramen in Fishes. 513 



in a noi-th to south direction. The clay was fonnd to rest upon a 

 deposit of the nature of river gravel. 



The writer is of opinion that the clay is redistributed Boulder- 

 clay from the adjoining heights, and that the boulders were brought 

 down at the same time from the line of outcrop of the grit. 



He is led to this conclusion by the local character of the boulders, 

 the almost total absence of foreigners, and the character of the clay. 



The red and brown colour of the latter at its base seems to show- 

 that oxidation of the contained iron has proceeded for a longer time 

 than in the case of the uppermost clay. This would be expected if 

 the clay was redistributed, for the basement mass of clay must 

 have been the superficial clay of the heights. The enclosed sand 

 would also indicate the complete disintegration of boulders of grit- 

 stone, etc., whilst the clay was in its primary position. 



The amount of disintegration which has taken place since redis- 

 tribution is marked by the crumbling surface of the large boulders. 



The general direction of the boulders may be explained by noticing 

 that the river flows from north to south. 



I^ E "V I E AAT S. 



I. — Pineal Fontanelle of Placoderm and Catfish. By Bash- 

 ford Dean, A.M., Ph.D. Nineteenth Eeport of the Com- 

 missioners of Fisheries of the State of New York, pp. 307-363, 

 pis. i.-xiv. (Albany, 1891.) 



DR. DEAN, as assistant to Prof. Newberry, of Columbia College, 

 New York, has had the privilege of studying the fine skulls 

 of Dinichthys described by the Professor. He has directed attention 

 more especially to the pineal region of the cranial shield, and now 

 attempts to show, from a study of the pineal foramen in the 

 Siluroids, that the well-known foramen in Dinichthys and its allies 

 must have been the seat of a median eye. The aperture is remark- 

 ably minute, and after a detailed description of the surrounding 

 bone, Dr. Dean remarks that this foramen " becomes naturally the 

 pinhole of the camera to produce an inverted image upon the retina, 

 a condition almost unparalleled for primitive simplicity, obviating 

 as it does a diaphragm (iris), as well as the specialized humours, 

 aqueous, crystalline, and vitreous. Moreover, it will at once be 

 seen to do away as well with all devices for accommodation, since 

 the focal distance would be practically the same for a point at any 

 given distance." The author's numerous dissections of the soft 

 parts of the Siluroid head afi'ord material for a valuable series of 

 notes and figures ; and it seems to be demonstrated that the pineal 

 eye exists in a very degenerate condition. At the same time, we 

 fail to recognize in the new memoir any additional evidence in 

 favour of the supposed genetic connexion between the Coccostean 

 fishes and modern Siluroids. Dr. Dean's researches merely result 

 in the plausible explanation of a feature in the cranial roof of 

 Dinichthys, by reference to a nearly analogous structure in an 

 existing type of fish. A. S. W. 



DECADE III. — VOL. VIII. ^NO. XI. 33 



