SEXUAL CHARACTEES — ELASMOBRANCH FISHES 193 



The streak marked K in the figure has been misinterpreted as 

 a clasper, an error which, owing to the influence of E. Stromer 

 von Reichenbach, has found its way into the text-books. How- 

 ever, this is the only specimen in which this streak occurs, and, 

 further, as recently as about 1914 at the points marked * in the 

 figure. Doctor Woodward has caused excavations to be made 

 and microscope shdes prepared of the abstracted fragments. 

 These sections reveal the same structure as that of the kidney of 

 recent forms, the organ having become calcified. 



There being no claspers, it is a safe assumption that there are 

 also neither clasper siphons nor clasper glands. 



PLEURACANTHUS PARALLELUS 



Subsequently, in late Palaeozoic times, there appeared elasmo- 

 branchs with claspers — the Pleuracanthei. Figure 2 represents 

 the specimen from the Carboniferous 'gaskohle' at Tfemosna 

 near Pilsen. I have not seen this fossil. Dermal denticles 

 appear to be preserved, and, if the restoration of Xenacanthus 

 decheni is to be rehed on, the spoon-shaped conformation at the 

 tip of the claspers had already been evolved. 



The point of interest is that the clasper, from its skeleton, 

 appears to be of the 'straight' or 'direct' type, by which is meant, 

 not that it is without a gentle curve longitudinally, but that it is 

 not rolled up in a scroll-like manner; on the contrary, the groove 

 is very wide open. Such a condition I interpret as being primi- 

 tive here, and secondary in the skates. The type of clasper 

 suggests that possibly clasper siphons were not yet evolved, or 

 were present only in a rudimentary form. 



Acanthodes wardi is devoid of claspers, and therefore of no 

 use in this investigation. 



SQUALORAJA POLYSPOXDYLA 



This early Mesozoic chimaeroid fish, to be compared subse- 

 quently with Chimaera, is beautifully preserved in the specimen 

 P 2276 found in the lower lias at Lyme Regis, Dorsetshire, Eng- 

 land, a Jurassic formation (fig. 3). 



