ON THE APPENDICES GENITALES (CLASPERS) IN THE SELACHIANS. 31 



The terminal pieces are 5. 



The dorsal one, Td, is somewhat s-shaped, round, and articulates medially with the end-style, 

 while the hindmost part of it projects through the skin as a curved, polished claw; as in Acanthias, 

 it is united with a thin lamellar piece, Td^, which piece, with the exception of the hindmost point, is 

 quite covered by the skin forming the dorsal lip of the furrow. 



The ventral piece Tv is also somewhat s-shaped, broader than the dorsal one, thick at the 

 base, becoming thinner distalh' and lateralh'; it is concave like a spoon on the side towards the 

 furrow, on the other side rounded. At the proximal part of the lateral edge it is firmly united with 

 a hard, dentine-like piece Tv^^ which in ^icautliias is onh- represented by an uncalcified mem- 

 brane. This piece is before (proximally) prolonged to a long, flat end, behind (distally) to a shorter 

 one, projecting through the skin as the before mentioned claw in the ventral lip of the furrow; the 

 piece is rather narrow, ventrally concave, dorsally rounded. In moving it follows the piece Tv. 



The last piece T', corresponds to the thorn in Acanthias and Somniosus ^ and is also here 

 formed as an elegant, bent, rounded and completeh' smooth thorn with the proximal end head-shaped. 



It is quite out of the question that these <: claws , as supposed by Kroyer, should be able to 

 act as a (prehensile organ , as the}- cannot properly be moved against each other; but the>- will be 

 very able to fix the appendix firmly in a hollow, as by the dilatation of the terminal part their points 

 are turned in three opposite directions, as may be seen from fig. 6 in the text. 



The muscular system. From the M. adductor has been separated a long, flat bundle as a 

 particular muscle originating before from the medial aponeurotic stripe together with the other 

 fibres of the M. adductor^ and then on the dorsal side passing obliquely over the AI. extensor and 

 next over the M. dilatator \ on the appendix it follows the appendi.x-slit , and forms together with the 

 M. dilatator the medial lip of this slit; partly it is attached in the skin of this lip, but chiefly on the 

 proximal end of the piece Td^. This muscle evidently is instrumental in increasing the dilation of 

 the terminal part, which dilation, as has alread}- been indicated, seems to be especially great in Spinax. 



The M. extensor is almost as in Acanthias, that is, not sharply bounded from the dorsal part 

 of the il/. dilatator. 



This latter, on the contrary, is on the ventral side distinctly bounded from the M. adductor 

 by a line running obliquely from the lateral side down towards the medial side. Its aponeurosis, as 

 in Acanthias, is especially attached to Td and Tv. 



The glandular bag (the M. compressor) does not in any of m}- numerous specimens reach quite 

 to the pelvis, and accordingly it must be termed proportionally small. Its <outer lip-muscle as usual 

 originates from the piece /J and the hindmost rays, and is with its principal portion \-er)- distinctly 

 inserted on the piece Tv^, with another portion on the folded part of the ventral marginal cartilage 

 (not on the thorn T^j. 



Scymnus lichia Bonap. 



A skeleton in the Zoological Museum (from V. Fric in Prague). 



In this specimen the appendix only reaches a trifle farther backward than the fin-membrane, 

 and the condition of the terminal skeleton makes it probal:)le that the organ is not fully developed. 



