382 PEOF. G. B. HOWES ON THE 



intervening arteries (the [anterior or superior] mesenteric, 

 lieno-gastric, and anterior spermatico-mesenteric, of authors) * 

 may for the present pass without further comment ; the accom- 

 panying figures show them (a.sm.) to be variable in point of 

 origin and in mutual relationship ; not so, however, with the so- 

 called inferior (posterior) mesenteric (a.sm. of fig. 1). That 

 vessel invariably arises, in Batoids and Selachoids alike, some 

 distance in advance of the processus digitiformis and so-called 

 rectum (dv" and i.l. of fig. 1) ; it lies within the suspensory 

 ligament of these structures and passes obliquely backwards and 

 downwards, to reach the first named of them : on doing this it 

 breaks up to form an elaborate system of vessels which are 

 restricted to the appendix and to portions of the gut imme- 

 diately adjacent (cf. fig. 1). In the long-bodied Selachoids 

 this vessel usually supplies the above-mentioned parts alone ; 

 in some of them, however (ex. Mustelus [Parker, 27. p. 701]), as in 

 the laterally extended Batoidei f, it sends branches to the genital 

 glands, as is expressed in Parker's term "posterior spermatico- 

 mesenteric " applied to it %. Be the branches and facts of dis- 

 tribution of this artery what they ma}* §, its main trunk is invari- 

 ably disposed as above described ; it is primarily related to the 

 posterior segment of the intestine with its appendage, and its 

 most striking feature is its constant origin at a point remote from 

 these anteriorly — consequent upon which it takes the said back- 

 ward course. 



I have recently published elsewhere || some observations in 

 ichthyotomy that have extended over several years, in connection 

 with which I have had occasion to inject a large number of 

 Skate. While doing so, my attention became arrested by the 

 occasional presence of one or more arteries passing from the 

 dorsal aorta to the intestinal canal posteriorly to the region 

 alluded to above, in addition to the paired vessels already de- 

 scribed {ante, p. 381). The only mention of such vessels which I 

 have been able to find is one by Hyrtl for the Torpedo, in which he 



* Cf. Hyrtl (18), Parker (27), and Marshall and Hurst, ' Practical Zoology,' 

 ed. 2 (London, 1888), pp. 234 et seq. 



t Cf. fig. 1, a. g., and Parker's ' Zootomy,' p. 62, fig. 20. 



J 27. p. 701. 



§ It distributes branches into the suspensory ligament which lodges it ; and, 

 from these, twigs may pass to the genital ducts, especially in the female. 



II Jom-n. of Anat. and Phys. vol. xxiv. (n. s. vol. iv.), pp. 407-422 (1890). 



