ON THE APPENDICES GKXITAI.I.S iCl.ASPERS) IN THE SELACHIANS. 55 



deep hollow on the outer, otherwise rounded surface, by which means a strong ridge is produced on 

 the opposite, concave inner surface, and this ridge is firmly connected with the raised medial edge 

 of the piece To; the above mentioned deep lateral pocket is then situated between the last-men- 

 tioned pieces. 



The muscular system is peculiar by the little marked bounding between the single groups 

 of muscles. Thus on the ventral side the fibres of the M. adductor are seen behind and medially to 

 continue, without any bounding whatever, directly into the M. dilatator, and laterally to pass over on 

 the M. compressor in such a way, that the contour of the glandular bag before and medially is quite 

 effaced; the fibres of the ventral wall of the glandular bag — as in Torpedo -- have the same direc- 

 tion as those of the M. adductor, and they are here, until close to the lateral edge, quite woven 

 together with the latter. On the dorsal side the marginal portion of the M. adductor is seen as a 

 powerful mass arising partly from the pelvis, partly from the aponeurotic covering of the muscles of 

 the abdominal wall, and laterally overlapping part of the M. extensor. This latter arises from the 

 whole extent of the basale, as well as from the following pieces, and is distally, without any bounding, 

 woven together with the M. adductor and the continuation of this, the M. dilatator, which latter also 

 with a considerable mass wraps the whole of the appendix-stem and both the marginal cartilages 

 quite to their margins at the appendix-slit. Behind it is attached to the proximal edge of the ventral 

 covering pieces (v , v T ). The part of the M. compressor, appearing as the outer lip-muscle, is only 

 sligthly developed; more developed is the part of the dorsal muscular wall of the glandular bag, 

 running more transversely, and wrapping the glandular body, which it follows throughout the shaft 

 to its hindmost end at the terminal part. 



The glandular body stretches here -as in the preceding genera of Rays — through the 

 whole length of the shaft along the ventral marginal cartilage, constantly tapering backward, and 

 the furrow which in the part of the body, situated in the bag, runs from before obliquely to 

 the medial side (separating a pigmented and an unpigmented surface), continues with its pores 

 quite to the terminal part. The part of the appendix-slit situated in the terminal part, has quite 

 smooth walls. 



The above described features of the glandular body, and several other characteristics — as for 

 inst. the presence of ventral covering pieces, enclosing a pocket with an opening through an outer 

 side-slit, and furthermore the hollowing of the ventral side of the piece To -- very much recall those 

 in Torpedo and Rhinobatus 1 ), and it is evident that Trygon is more closely allied to those than to 

 Raja, at all events with regard to the structure of the appendices. 



Raj idee. 



In this family the appendices reach to quite a considerable size, and consequently they, natur- 

 ally enough, have attracted the attention, and have in some species several times been the subject of 

 examination. As a rule, however, this examination has not been very thorough, nor has it been ex- 



') Partly even those in Rhina. 



