A. Smith Woodward — Affinities of Cydohatis. 509 



3. There are no traces of median fins. — In the TorpedinidEe, these 

 fins are always more or less developed, one or two dorsals being 

 invariably present, except in Temera, and in this genus the caudal 

 fin is well represented. In the Trygonidse, on the other hand, the 

 presence of median fins is an exception to the general rule, dorsals 

 never being met with, though sometimes replaced by barbed spines. 



4. The sMn is armed loith spinous tubercles. Though not previously 

 observed, the National fossils demonstrate very clearly that the 

 dorsal surface of Cydohatis was provided with at least one median 

 row of prominent spines, and there are numerous minute prickles 

 scattered both over the trunk and fins. 



The larger tubercles are best seen in the type-specimen of C. 

 major (the rough impressions of a few being shown in Miss Wood- 

 ward's drawing, loc. cit.) ; in another fossil (B. M. No. 49514) which 

 Mr. J. W. Davis has also labelled as pertaining to the same species ; 

 and in an incomplete specimen of C. oligodactylus (No. P. 99). The 

 first of these shows that the series was continued forward almost 

 as far as the pectoral arch, though the tubercles in advance of the 

 pelvic arch appear to have been much smaller than those behind, 

 and they succeed one another at short intervals. Each of tliese 

 dermal defences is oval in form, rising into a sharp spine; and those 

 placed more anteriorly have the base radially crimped, while the 

 posterior examples seem to have been smooth, with the spine much 

 more laterally-compressed and thorn-like, and the apex directed 

 backwards. In one small fossil (No. 49557), of doubtful species, 

 the tail has the appearance of being completely encased in rows of 

 the tubercles. 



The minute, irregularly-scattered prickles may be most satisfactorily 

 studied in Nos. 49556, 49557, and 49514, their shape and characters 

 being best displayed by the first-named, and their distribution by the 

 two latter. Each of them seems to consist of a small erect, or back- 

 wardly-directed, spine, fixed upon a rounded, radially-marked base, 

 being, in fact, a miniature of a larger tubercle, but higher in 

 proportion to its size. There are some indistinct traces of these 

 structures in Egerton's original specimen of C. oligodactylus ; and 

 the example of C. major (No. 49514) already referred to shows 

 them densely arranged upon the margins of the pectoral fins. I 

 have discovered no other dermal calcifications, except the teeth ; 

 and the " small hexagonal shining dermal ossicles," mentioned by 

 Mr. Davis {loc. cit.), are evidently the superficial calcified tesserse of 

 the endoskeletal cartilage. 



None of the living "electric rays" are known to have the slightest 

 trace of dermal asperities, whereas the presence of these is a marked 

 feature of certain Trygonidaa — especially the genera destitute of 

 barbed caudal spines; and the facts just recorded are therefore 

 corroborative of the inferences drawn from the three previous 

 considerations, namely, that it is to the Trygonidee rather than to 

 the Torpedinidse that Cydohatis must be referred. 



It would thus appear that there is still no evidence of the existence 

 of Torpedoes in times anterior to the Eocene ; and the earliest 



