GENERA OF THE ARCIFEROUS ANURA. 99 



food; but I suspected they had been nibbled oiF by some Pomotes (Sunfish) confined 

 in the same aquarium, who, attracted by their rosy color, thought them lawful prey 

 There were very small stumps remaining, of which the two anterior, seventeen days 

 after my first observation, developed a minute brown fringe on the under side. 

 Twenty-four days later, the stumps were longer, and the two anterior now bore a 

 double series of processes, which were of a rosy slate color. The animal still came 

 to the surface for air, and disliked excessively to be removed from the water. It 

 measured 9 in. 9 lin. in length, and was at first pale brown, with numerous black 

 dots above, and pale slate below, — but became darker and the spots larger. There 

 was a golden band on the side of the lip and " cheek," and the toes were tijiped with 

 a corneous cap. Further observations went no further than to show that this Siren 

 could live for more than two months deprived of its branchias, and that the latter 

 can be reproduced. 



I have seen a specimen of the Siren striata in which the branchial 

 fimbrite were thickened, and the three main rami adherent throughout their length 

 to the pharyngeal walls between the fissures ; being thus entirely abortive and in 

 part atrophied. In skeletal and other features, this species does not differ from the 

 Siren lacertina. 



Another feature characteristic of the immature stages of both tailed and tailless 

 Batrachia, is permanent in the " perennibranchiate " types just mentioned, and in the 

 Amphiuraa and Protonopsis, — i. e., the cartilaginous condition of the intervertebral 

 tissue, and consequent retention of the biconcave or fish-like vertebra. It does not 

 appear to have been previously pointed out that this feature persists in all the species 

 of the American types Amblystomidge and Plethodontidae, contrary to the condition 

 in the forms of the Old World. 



Prof. Baird, in the first synopsis of our genera published, pointed out the difierence 

 between Amblystoma and our other genera, in the ossification of the tarsus and 

 carpus of the former, and cartilaginous state of the latter. This is again a strictly 

 developmental difference, identical with the Perennibranchiates and extinct 

 Xenorhachia. 



With respect to the cranial and tarsal ossifications, the Siredon is first identical 

 with the larva of Amblystoma, — e. g., p u n c t a t u m, — when half tlfe dimensions of 

 the adult ; bearing distinct nasal and prefrontal bones with maxillaries, and the 

 longitudinal palatines with a slight ligamentous connection with the reduced ptery- 

 goids, forming an arch separate from the parasphenoid. In so772e Siredons the carpal 

 and tarsal bones are fully ossified, — a condition which I have not yet observed in any 

 Amblystoma larva. 



The structural features of Necturus are very different, as has been in part pointed 

 out by authors, and are identical loith those of the larva of Spelerpes rubra and salmo- 

 nea. Both types lack the maxillaries, nasals and prefrontals, and exhibit a broad 



