124 TRANSACTIONS OF THE [FeB. 23^ 



eum of Columbia College. This author finds, in fact, that 

 the fins of " Gladodus " afi^ord no evidence as to lateral fold 

 origin, asserts the presence of basal plates, and adduces the 

 structure of the ventral fin to support his view as to the 

 essentially modern character of the paired fins. The unique 

 character of the body terminal as figured by Newberry, Jaekel 

 regards as the restoration (in a grajihite oil color) of the 

 collectoi". While he emphasizes the modern structural charac- 

 ters he notes, however, the phylogenetic importance of the 

 circum orbital ring of derm plates (Acanthodian). 



At the present time discovery of new material by Rev. Wm. 

 Kepler, of New London, Ohio, has enabled some of the 

 structural characters of this interesting shark to be more 

 critically examined. And in a paper, now in publication, the 

 present writer has endeavored to consider the essential charac- 

 ters in their relation, particularly, to the doctrine of lateral 

 folds. 



It would appear in summary that this shark form (which the 

 writer distinguishes from the Cladodus of Traquair, in which a 

 monoserial archipterygium is present, by the new genus 

 Cladoselache), presents the most manifest evidence as to the lateral 

 fold origin of the paired fins. The fins, as stated by Smith 

 Woodward, are actual remnants of the derm fold. The 

 unjointed rod-like radials proceed from body wall directly to 

 the fin margin ; the fin surface, therefore, is as yet lacking the 

 specialization of the dermal margin and dermal rays. It would 

 now appear that the basal plates exist but in a most primitive 

 condition ; their fusion into a plate is seen to occur to a partial 

 degree in the pectoral fin, but the rotation outward of the 

 posterior end of this trunk of basals does not as yet take place ; 

 the entire fin stem is still imbedded in the body wall. In the 

 ventral a most interesting condition occurs, — a more primitive 

 arrangement would here very naturally be expected, — the 

 hasals in the body wall are a.s yet unfused, and are represented by 

 rod-like bars of cartilage, which outwardly resemble basal joints 

 belonging to the radials — and were, in fact, so interj^reted by 

 Jaekel. The proximal ends of the basals are in actual process 

 of concentration near the anterior fin magin ; the radials, 

 however, are still more or less at right angles to the axis of the 

 fish. Smith Woodward has already recorded one of the most 

 significant features in the fin structure, — the marked way in 

 which the radials are crowded together side by side in the 

 anterior fin margin, — giving rise, in fact, in the pectoral to the 

 specialization of a compact cut-water. The writer suggests that 

 this tendency to compress the radial elements in the anterior 



