210 DR. R. ■W. SHTIFEI.DT ON [Apr. 1, 



is found in the other. The latter develops the usual extra-, infra-, 

 and snprastapedial processes, while the last-named sends off a small 

 special apophysis of its own that lies in the epithelium linin;^ the 

 infernal surface of the ear-drum. Mesiall}', the columella auris is 

 slightly enlarged, tipped with cartilage and closely fitted into the 

 fenestra ovalis. Upon properly opening the dense, flinty, osseous 

 otic capsule, I find a sacculus of fair size and with the tliree semi- 

 circular canals disposed somewhat as they are in Lacerta. The lagena 

 is moderately well developed, hut shows harely any inclination to 

 liecome spiriform. Bej'ond tlicse casual observations I made no 

 special note, in so far as the auditory organ was concerned. This 

 apparatus widely varies in the Lacertilia, and to make correct and 

 exhaustive dissections of these parts requires much time and abun- 

 dance of material, neitlier of wbich are quite .ns I would have them 

 at present. 



XI. A TRW BRIEF Notes upon the Arterial System, 



Upon examining tlie dorsal aorta below the heart, it is seen tliat in 

 its Ijranching it is inclined to throw off lather a generous sup|)ly oi' 

 offshoots. At the point where the coeliaco-mesenteric is usuallj- given 

 off, two arteries arise — the hepatie, which thereafter gives off smaller 

 mesenteric brandies; and, secondly, a coeliac, which chiefly supplies 

 the stomach, the spleen, and the pancreas. About a centimetre below 

 the point where the coeliaco-mesenteric comes away there is given 

 off a large mesenteric brancli, which with its branches furnishes the 

 jirincipal arterial sufiply to the intestine and its supporting mesen- 

 teric membrane. A few smaller mesenteric offsiioots are sent forth 

 at irregular distances below this point. Branches from these, as well 

 as from the dorsal aorta, still more posteriorly, supply the retrahenfes 

 costarum muscles and less important structures along the region of 

 the spine. The ovarian branches exhibit no special peculiarities. 

 There may be as many as seven renal branches upon either sirie ; a 

 generous supply of lia-morrhoidal arteries are also thrown off; while 

 a vesical branch to the bladder is supplied by the right common iliac. 

 Posteriorly, the dorsal aorta is continued to the end of the tail as the 

 caudal aorta, and for the entire lengtii of this appendage it passes 

 between the arches of the chevron l)ones. 



I made no es])ecial research for the existence of the retia mirabilia 

 along the caudal portion of the vertebral column in this lizard, but 

 have reason to believe that if such vascular anastomoses there occur, 

 in our subject, they will be found to be not very markedly developed 

 in the region to which we have referred. It is generally understood 

 that a rete mirabile is more likely to be discovered along the vertebral 

 column in the tail of those forms of Lizards and Blindworms wherein 

 that structure is often lost through some mishap and nature repro- 

 duces the appendage again. This is especially true of the Blindworms, 

 It is not likely that our thick-tailed Heloderma often parts with 

 that extremity of its body ; it is nevertheless true, however, that 

 when it does, nature supplies a new tail in precisely the same manner 

 as vve see it reproduced in other Lizards similarly gifted. 



