186/.] MR. ST. GEORGK MIVART ON PLETHODON PERSIMILIS. 695 



In the heart of the Hippopotamus dissected, a very faint mark 

 existed of the above-named division, but this would be entirely obli- 

 terated, I believe, in the adult animaL Dr. J. E. Gray places the 

 Hippopotamus under Elephantidce, and thinks that the form is allied 

 to the Halicoridce; but I fail to see the resemblance. The muscular 

 band in the inferior cava described by Gratiolet is probably not found 

 in the other pachyderms. 



Brain. — All the pachyderms, with the exception of the Elephant, 

 have small brains ; that of this young Hippopotamus, as before 

 stated, weighed 10| oz., and probably in the adult animal it would 

 not exceed 20 oz. In an Elephant, weighing about 3 tons, I found 

 the weight of the brain to be 12 lb. In a Tapir {T. americanus), 

 weighing about 140 lb., the cerebral mass was 7 oz, 380 gr. In the 

 Horse the brain weighs about 16 oz. In the Pigs it varies from 5 

 to 7 oz. In the Rhinoceros, as described by Professor Owen (Trans. 

 1862), the brain weighed 1 lb. 14^^ oz. In the other members of 

 the Hog family, and in the Bahirussa, Peccaries, Hyrax, Zebra, 

 and Quagga, judging from the skull-cavities, the brains are of small 

 size, indicating to a great extent the slight amount of intelligence of 

 these animals. 



From the above comparisons, as regards the visceral anatomy of 

 the Hippopotamus, it will be seen that the animal differs in many 

 important particulars from the other members of the pachyderm 

 family. In my next paper I hope to investigate the microscopic 

 anatomy of the intestinal tube, and to compare the osteology of the 

 Hippopotamus with that of the other pachyderms. 



3. On Plethoclon persimilis of Gray. 

 By St. George Mivart, F.L.S. 



In the Zoological Society's 'Proceedings' for 1859* Dr. Gray 

 described and figured a species of Newt, said to be from Siam, under 

 the name Plethodon persimilis. The author justly remarked its 

 striking similarity in size, form, colour, &c. to Plethodon ylutino- 

 sus of North America, adding that he was at first inclined to believe 

 that the specimens described were really American, and had been 

 sent to Siam. From its great resemblance to the last-named species, 

 Dr. Gray included the new one in the genus Plethodon. 



Dr. Giinther, in his * Reptiles of British India'f, described again 

 the typical specimens ; but while noticing certain differences between 

 them and Flethodon glulinosus, yet retained the species in the genus 

 Plethodon. 



Having recently had occasion to examine the specimens of Urodela 

 preserved in the British Museum, when I came to the type speci- 

 mens of PI. persimilis, while struck with their similarity to specimens 

 of PL glutinosus, I was startled by their alleged habitat. 



* Proc. Zool. Soc. 1859, p. 2:50, pi. xix. f. 2. 

 t ISfU, p. 439. 



