622 MR. F. E. BEDDARD ON THE [May 29, 



anterior abdominal takes place almost exactly on the middle of the 

 stomach, as also in an example of Alligator onississippiensis with 

 which I have been able to compare this Caiman. Moreover, in both 

 Alligators the right branch received a twig from the stomach which 

 underlay (when the reptiles were examined in the usual position of 

 dissection) the left division of the left anterior abdominal. The 

 same branching is described by Jacquart in the " Caiman a museau 

 de brochet," but the details seem a little different. 



The material does not at present exist for a comparison of the 

 different genera of the Crocodilia, and for a classification based 

 upon the entire structure of these reptiles. It is in the meantime 

 interesting to note — though it is obviously premature to found 

 any generalisation upon the facts — that the West African Osteo- 

 Iceonus does show certain points of likeness to the American 

 Crocodilia in respect of some of the veins that have been 

 dealt with in the foregoing pages. In Alligator, as shown by 

 Jacquart's figure oi Alligator lacitis*, and by my own observations, 

 which I take the opportunity of recording in the present 

 communication, upon A. mississipjnensis, the two anterior 

 abdominal veins are not connected by an obliquely running 

 commissure t. The same vein is also absent or at least modified 

 in Caiman sclero2:>s. On the other hand, as I have shown, certain 

 species of the genus C^^ocodilus possess it. Xow this connecting 

 vein is absent or at least modified in Osteolamiiis. Again, the 

 latter genus has the two azygos veins exposed superficially along 

 their course, while in Crocodilus the same veins are for the most 

 part entirely buried under the musculature. In this particular 

 also Osteolcemus agrees with the species of Alligator which I have 

 referred to in the foregoing pages, viz. Alligator onississippiensis. 



Dorsal and Lateral Parieto-hepatic Veins. — These veins, tei-med 

 by Rathke venfe vertebralis postrem^e, really consist, as was not 

 noted by him, of veins arising from two sources. There are A^eins 

 connected with the vena vertebralis posterior or azj^gos, on each 

 side, or, if the latter be not visible superficially, emerging from the 

 parietes close to the vertebral column, and there ai'e trunks of more 

 lateral origin from the parietes. Save for the VaranidfeJ, this 

 double origin of the dorsal parietal affluents of the hepatic portal 

 system is not found among the Lacertilia, or at least has not been 

 as yet recorded, and certainly does not exist in many forms. The 

 presence of the lateral parieto-hepatic affluent is accompanied in 

 both the Crocodilia and the Varanid^e by the development of a 

 longitudinally running lateral parietal vein, which, though re- 

 presented in the Lacertilia, is not so important in them. I have 

 already given some accoimt of these veins in Crocodilus acutus §. 

 I am now able to give further details of this, system in the 

 Crocodilia from the examination of other species. 



* Ann. Sci. Nat. loc. cit. pi. 3. fig. 1. 



t It is noteworthy that in both All. mississippiensis and Caiynati sclerops the left 

 vein is nearer to the middle line than the right vein. 



X Supra, p. 616. ■ § P. Z. S. 1905, vol. ii. p. 466. 



