ON THE APPENDICES GENITAI.1-S (CLASPERS) IX THE SELACHIANS. 59 



style 1 ) (to judge by the pieces before me this part seems to be a little varying- with regard to the 

 details of the processes). 



As to the muscular system the reader is referred to Raja clavata with which the other 

 Ra/a-species agree exactly in most respects. The M. dilatator, however, is here somewhat more 

 distinctly than in the thorn-back separated into two, a large dorsal one, and a smaller ventral one. 



The glandular body, as in all AV/7-species, is limited to the dorsal side of the ventral 

 bag proper, and accordingly does not continue into the shaft. In young specimens of the Skate with 

 undeveloped appendages not yet reaching the end of the ventral, the appearance of the gland is 

 rather deviating from that of the developed one; it is more flattened, and the gland-pores are spread 

 in more (four or more) rows over the greater part of the surface; in other words, it shows a rather 

 striking resemblance to the glandular body in Rhina. By a continued growth of the marginal por- 

 tions of the gland, and by a strong rounding of these portions, the surface that in younger animals 

 is provided with pores, will be hollowed, and thus apparently become more narrow, and in this way 

 the characteristic deep longitudinal furrow will arise. 



Raja nidarosiensis Collett. 



Of this species I have had only one pair of dried ventral skeletons, the appendix-part of which 

 had a length of abt. 33 cm . The principal features agree exactly with those of the Skate; the resem- 

 blance includes the common habit of the single skeletal pieces, but a closer examination of these will 

 show some minor peculiarities in the details; for inst. it will especially easily be seen that the piece 

 T z is bent in a somewhat different way, and has a relatively larger lateral wing, a larger forward 

 directed tap, and its distal end has not the peculiar shape like the blade of an axe; on its medial 

 surface it is deeply concave, spoon-like, etc. I shall however omit to give a detailed account of the 

 deviations of all the pieces from those in the Skate, and leave to others, who may have more material 

 at their disposal, to work out this subject more thoroughly; no doubt the deviations will make good 

 specific characters. According to the existing descriptions of the species the appendages are very 

 large, and are said to reach behind to the beginning of the first dorsal fin. 



Raja clavata L. 



(PL IV, fig. 49-52; Pl-Vl, fig.6 7 -6S.) 



This Selachian I think to be the one whose appendices have most frequently been examined 

 and described. Duveruoy 2 ) has briefly mentioned them, their glandular bag with its glandular body 

 and their skeleton, the nomenclature of which he has formed in accordance with the appellations of 

 the parts of the hind limb and the foot of a mammal. Later they have been described by Vogt and 

 Pappenheim 5), whose description it is rather difficult to use on account of the want of references 



J ) Iu my figure it has been displaced a little, so as to reach too far up on the other terminal part. 



2) Cuvier: Lecons de l'anatomie comparee, 2d ed., vol. S, 1846, p. 305 (perhaps the description applies to R. circularise). 



3) Rech. sur l'anat. comp. des organes de la generation chez les animaux vertebres. Ann. sc. nat. (Zool.), vol. XII, 

 1859, p. in — 117, pi. 3. 



