AND MESOZOIC FISHES. 
429 
Fig. 1. Xenaoanthns deefienii (joW. From Fritsch, 4ei' (iaskoiile ii. ti. Kalksiciii 
mens. Much reduced. 
known from beds older than the Coal Measures, while Selnchii are Uiiowii Iroin the 
Devonian. 
The structure of the paired fins here i)oint( d out snstuins the views alrea<ly 
announced by Mr. Bashford Dean in the paper (pioted, and this author is to 
be congratulated that the view which he has put lorth is so lully sustained hy 
the material now described. One hypothesis which he holds rtapiires lurther <‘(in- 
tirmation, viz.: that the metaptorygiuin is formed by the fusion ol tlie basal ele- 
ments. The extensive fusion seen in the later genus AVwwerh/?;/ as compared 
with the earlier genus Cladodiis supports his position so tar as it go(-s; hut tlie 
origin of the primitive segments is not thus explaineil. 
Mr. Dean refers Cladodiis fylerii to a genus distinct from CUidodns, which 
he calls Cladoselache. The character ot the (ims does not seem to dilfer Irom that 
ascribed to Cladodiis by Trarjuair, and the geological horizon is tliat ol tin* latti’r 
genus. 
Mr. Dean thus states his conclusions, (1. c.): — 
“It would appear that this shark form presents the most manifest eviileiice as 
to the lateral fold origin of the paired (ins. The fins, as state<l hy Smith Woodward 
are actual remnants of the derm fold. The unjointed rod-like radials proceed from 
the body wall directly to the lin margin ; the fin surface. tlu>refore, is as yet lack- 
ing the specialization of the dermal margin and dermal rays. It would now apimar 
that the basal plates exist but in a most primitive condition ; their liision into a 
plate is seen to occur to a partial degree in the pectoral lin, but the rotation out- 
ward of the posterior end of this trunk of basals does not as \-et 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 lunv vi-ry naturally be 
expected,— hsals in the body xvall are as yet tinfused. and are represented 
by rod-like bars of cartilage, which outwardly resemble basal joints belonging to 
the radials. and were, in fact, so interpreted by Jaekel. The lu-oximal ends of the 
basals are in actual process of concentration near the anterior lin margin ; the 
radials, however, are still more or less at right angles to the axis of the lish. 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 hy side 
