68 ON THE STRUCTURES AND DISTRIBUTION OF THE 



of the same group exhibit a degraded or obliterated auditory apparatus ; but this 

 feature is not uniformly coincident with the preceding ones. (7.) The xiphisternum 

 is formed of divergent limbs ; in the bulk of the tribe it is an emarginate cartilagi- 

 nous plate, and in the opposite extreme an osseous style, as in the Eanidge. 



Of these features, the first, third, fourth and sixth are agreements with, or approxi- 

 mations to the structures of the same elements of the Salamanders ; the resemblances 

 are borne out in the physiology of the same types. 



In the observed examples of the above types, that is, of the Discoglossidse, Pelody- 

 tidse and Scaphiopodidge, the eggs are deposited in small clusters, ( Pelody tes) , a short 

 thick loop, (Pelobates), or in a series with a slender, tough, thread-like attachment, 

 (Alytes). In the family following that of the Pelobates, that is, the New World tree- 

 toads, the eggs are, in the only Old World species, — Hyla a r b o r e a , — deposited in 

 globular masses, as among the Ranidse, but much smaller; while in our Hyla 

 pickeringii the masses include but from four to ten eggs. In the first mentioned 

 forms, the male seizes the female in front of the arms, while in the remaining and 

 major number of species, as well as in the observed Eaniformia and Bufoniformia, 

 she is seized round the axillse. 



In respect to the deposition of eggs, the peculiarity mentioned is an approximation 

 to the mode observed by the Salamanders, which are deposited singly in the water 

 (Triton, Notophthalmus)* on leaves, or on the land, connected by a tough thread 

 (Desmognathus) . Salamanders also seize the female in advance of the arms, but 

 with the hind limbs; (Notophthalmus, Triton). 



Additional peculiarities in the development of Alytes, Pelodytes,t Cultripes and 

 Pelobates are, that they spawn at two seasons instead of one, and that their larvae 

 attain a larger size than those of other Anura before completing their metamorpho- 

 sis. This latter feature is, however, repeated near the other end of the series — 

 among those with cylindrical pelvic supports, in the genus Pseudis. What the 

 significance of these peculiarities is, and what their coordination with structural 

 characters, is not yet known. 



The occurrence of a xiphisternal style similar to that of the Ranidae, may be re- 

 garded as an indication of superiority, not only in consideration of • this affinity, but 

 as a greater degree of specialization and ossification of the part. It appears, how- 

 ever, not merely among the most Raniform Arcifera, but among some with procoelian 

 vertebrae, which have the salamander-like mode of reproduction, and also among 

 some of the opisthocoelian species. 



* Notophthalmus viridescens lays its eggs singly on leaves, e. g., at the union of the capillary segments 

 of Myriophyllum, or along their length, pressing them together on the egg as it is deposited. They adhere 

 closely to its gelatinous surface, and serve to conceal it. 



t Thomas, Ann. Sci. Nat. 1854, 290. 



