2 4 o SCIENCE PROGRESS 



PALEONTOLOGY. By W. P. Pycraft, F.Z.S., A.L.S., F.R.A.I., British 

 Museum (Natural History), London. 



That the list of palseontological papers for the last twelve 

 months is a short one is but natural, having regard to the 

 troublous times through which we have just passed. Most 

 will agree that at the head of that list, in importance, must be 

 placed the Memoir on the Indigenous Mammals of Porto Rico, 

 Living and Extinct, by H. E. Anthony (Memoirs of the Ameri- 

 can Museum of Natural History, New Series, vol. ii, pt. 2). 



Bats are the only land-mammals now found in Porto Rico. 

 But in the remote past Insectivora, Rodents, and Ground- 

 sloths were represented. These, however, with one exception, 

 became extinct before the advent of man on the island. This 

 exception is found in the rodent Isolobodon, whose remains are 

 found, with fragments of pottery, in the shell-mounds which 

 bespeak a primitive people, and show that this animal was a 

 common source of food to these early inhabitants. The nearest 

 living representatives of Isolobodon are the Hutias (Plagiodon 

 and Capromys) of Cuba and Jamaica, and the South American 

 Coypu. 



The modern Agoutis are represented by two genera, Heter- 

 opsomys and Homopsomys ; though the author is of opinion 

 that these must ultimately be merged into a single genus. 

 But be this as it may, they are more nearly related to living 

 forms than any others of this island save Isolobodon. 



More important, from the palaeontologist's point of view, 

 are the remains of two large Chinchillids, Elasmodontomys 

 and Heptaxodon. These present striking peculiarities of den- 

 tition, and seem to have been derived from South American 

 ancestors ; the living Chinchillids having developed along 

 other lines, and being in many respects less specialised. 



Perhaps the most interesting of all the remains which this 

 island has yielded are those of the Insectivore Nesophontes, 

 and the Ground-sloths Acratocnus. 



Nesophontes represents an exceedingly primitive type, 

 widely separated from any existing Insectivores. This much 

 is shown not only in the skull and dentition, but also in the 

 rest of the skeleton. No living Insectivore, indeed, has such 

 an assemblage of generalised characters, so that the gap be- 

 tween any of them and Nesophontes is very great. On the 



