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V. On the Morphology of the Skull in the Amphibia Urodela. 

 By Professor W. K. Parker, F.R.S., F.L.S. 



(Plates XIV.-XXI.) 



Bead June 19th, 1879. 



Species 1. — Salamcmdra maculosa. 



1st Stage. — Embryos from the Oviduct a week or two before the time of exclusion * , 

 1 inch long, with three pairs of feathery gills. 



_L HE embryo of the Spotted Salamander has large external gills, like the larvae of other 

 " Urodela Caducibranchiata," but in this stage they are at their fullest development. 

 They soon shrink when the larva is ripe ; in one of these earlier embryos, 1 inch 1 line 

 long, the left branchiae were just disappearing. These are the youngest I have examined 

 of this species ; they were not more advanced in development than the larvae of various 

 congeners only half their size. The chondrocranium gets a considerable start of the 

 bony deposits, and is rather massive ; yet, although massive, it is a curious piece of 

 open work (PL XIV. figs. 1, 2), both roof and floor being largely deficient of cartilage. 

 The cartilage itself is composed of very large cells, and when treated with an ammo- 

 niacal solution of carmine is an exceedingly beautiful substance, as seen through the 

 microscope, even with rather low powers. 



The skull at this sta°'e has already undergone a considerable amount of modification 

 by the coalescence of originally unrelated parts, and also by the growth of crests and 

 conjugational bands on parts that are homologous f . The originally distinct front and 

 hinder basal bands of cartilage now form one continuous tract on each side ; the foremost 

 pair, the trabeculae (tr), have united with each both before and behind, and also with 

 the hinder pair of cartilages — the parachordals, or investing mass {i.v). The latter 

 cartilages have united near the end of the skull with each other, laterally with the 

 ear-capsules, and in front, as just stated, with the hind part of the trabeculae, so that 

 the base of the cranial framework is now well laid down ; it is, however, but two thick 

 planks of cartilage fixed together, in front and behind, by cross bars in each region. 

 This is quite in conformity with the Urodelous type of chondrocranium, which is always 

 largely imperfect in the middle both below and above. 



The hinder or parachordal conjugation is a narrow and incomplete band (PL XIV. fig. 2, 

 i.v, nc), on which the notochord rests ; but the internasal band in front is much larger. 



* These and most of my specimens of this Amphibian were the gift of Mr. Tcgetnieier. 



t For an account of the earlier conditions of the skull in the Urodela I must refer the reader to my recent memoir 

 in the ' Philosophical Transactions,' 1877, plates 21-29, pp. 529-597. 



SECOND SERIES. — ZOOLOGY, VOL. II. 23 



