154 MR. F. E. BEDDxVRD ON A TARASTERNUM [Juue 7, 



with the dwindling hi'onchial rings, but with the vasculai- folds 

 ah'eady spoken of. Microscopical examination shows them to he 

 thick bands of musculai- fibres, which are not stiiated. The 

 direction of these bands is circulai-. but they occasionally send oft' 

 anastomosing bi-anches as is shown in the accompanying sketch 

 (text-fig. 28, p. 153). Occasionally, too, a small band detaches itself 

 from one of the main hoops and ends upon the wall of the lung. 

 Between the various bands the wall of the lung does not appeal' 

 to be muscular. Towards the posterior end of the lung this 

 arrangement is lost ; thei-e are no longei- separate hoops of muscle 

 but the walls are covei'ed with a single sheet of musculatui-e. 



It is deal- from the above description, which may be compai-ed 

 with that of Platynrns on p. 150. that the sti'ucture of the lung 

 difiers very considerably in the two species. In Platyitrus the 

 lung has retained to a much gi'eatei' extent its pulmonary function, 

 the lung-substance extending much furthei' back than in Hydrus. 

 The lung has, however, a less calibre, even proportionately, than 

 in Hydrus, and there is no ti-ace of so marked a convei'sion into a 

 '' swim-bladdei' " with special muscles effecting its contraction and 

 expansion as occui'S in Hydrus. In the latter genus, moreover, 

 the whole hing extends fui'thei- back in the body than it does in 

 Platynrus. 



6, On the Presence of a Parasternum in the Lacertilian 

 Genus TUiqva, and on tlie Poststerual Ribs in that 

 Genus. By Feakk E. Beddard, M.A., F.E.S., Pro- 

 sector to the Society. 



[Received June 3, 1904.] 

 (Text-figines 29 t 80.) 



The use of the teim " abdominal ribs " foi- the vential and 

 superficially placed cartilages, fibi'ous bands, oi' ossifications so 

 distinctive of certain gioups of Reptiles, is open to the objection 

 that the term " ribs " has already a definite meaning attached 

 to it. It implies cartilaginous, fibi'ous, oi' ossified I'ods which 

 have oi- have had a connection with the vertebi'al column, 

 whereas the so-called abdominal ribs have no relation whatever to 

 the vertebral column, but are purely "S'entral structures formed 

 between the plates of the ventral abdominal musculature. 

 Furthermore, the term "abdominal ribs" is actually in use as 

 descriptive of structures which' ai-e real ribs, and which have 

 nothing to do with what other authoi'S have called abdominal 

 ribs. For example, Mr. Boulenger, in his ' Catalogue of Lizards.' 

 has i-ef erred, uiidei- the name of abdominal ribs, to the ventral 

 region of ribs in the Geckos. Chania^leons. and some othei- forms, 

 lying behind the sternum, which meet, pair by paii-, in the 

 ventral median line, thus completing a series of hoops encircling 

 the abdoiiien. Inasmuch, as Di-. Gadow * justly points out, that 

 * Camhridge Natural History : Amphibia and Reptiles, p. 504. 



