16 MR. F. E. BEBDARD ON THE [JlUl. 17, 



These muscles are limited to the membrane of the stomach and 

 oesophagus, and do not extend behind the extremity of the lungs. 

 The bands of muscle vary in size. 



In Chlamydosaurus there are some differences in detail from 

 the conditions characteristic of Physignathus . The mesogastrium 

 is much more distinctly double than the mesogastrium in 

 Physignathus^ owing to the greater size of the stomach, which 

 lies across the doi'sal middle liver, instead of to the left only. 

 With this is associated not only the much more distinctly double 

 character of the mesogastrium, but its much greater muscularity. 

 The membranous intervals between the muscular strands are so 

 much reduced, that each mesogastrium looks like a thin muscle of 

 coarse texture. 



I have ah^eady mentioned that the umbilical ligament is not 

 muscular. If there are muscles in the pulmo-hepatic, pulmo- 

 parietal, and gastro-hepatic ligaments, they must be microscopic. 

 The mesentery proper has only muscular fibres at its very 

 beginning, and these run at least chiefly to the stomach. 



Amphibohiru,s is somewhat intermediate between Physignathus 

 and Chlamydosaurus. Thei'e is some development of muscle in the 

 umbilical ligament posteriorly, which for the most part passes 

 out upon the gastro-hepatic ligament and ends in contact with the 

 walls of the stomach, and not, so far as I can make out, upon the 

 liver. The posterior end of the pulmo-hepatic ligament is 

 similarly invaded by muscular strands. The mesogastrium is 

 very distinctly miiseular, but not so mai'kedly as in Chlamydo- 

 saurus, though perhaps rather more so than in Physignathus. 



That the Iguanidse and the Agamidse are very closely allied 

 families is admitted. It is not therefore without importance to 

 compare the conditions which obtain in Iguana in respect of the 

 invasion of the mesenteries by muscular tissue. I have examined 

 from this point of view two specimens of Iguana titherculata, and 

 find the following state of affairs : — The umbilical ligament is 

 absolutely single and does not divide into two sheets posteriorly ; 

 it lies entirely to the left of the gall-bladder and contains no 

 muscular fibres. The mesogastrium is invaded by a moderate 

 amount of muscular tissue, but none of the other mesenteries 

 that have been referred to in the foi'egoing account of vai'ious 

 types of Agamidse shows any such thick strands of invading 

 muscular tissue in Iguana as they do in some of the Agamidae. 

 It seems likely therefore that this character will be of some use 

 in framing descriptions of the several families of Lizards. 



Some Arteries in Uromastix *. — The epigastric arteries ori- 

 ginate in Uromastix., as in Iguana, from the subclavians. In the 

 former genus, the artery pursues a rather complicated course 

 before passing down the inside of the abdominal wall as the epi- 

 gastric artery. The main branch of the subclavian traverses the 

 sternal region and appears on the ventral surf§,ce of the sternum, 



* Sec Caloi'i, Mem. Ac. Bologna, 1863, p. -525, for other detail.^ of vaf?cnlar s3-frtem. 



