IlfSECTIVOKA. 345 



toothless whales are represented in the deposits of this age (Mio- 

 cene), the latter, however, apparently only by the rorquals or their 

 immediate allies (Balasnopterse) ; Cetotherium seems to have occu- 

 pied a position intermediate between the Mystacoceti and Odonto- 

 ceti. Of the latter the earliest representatives appear to have been 

 the genera Ziphius and Mesoplodon, although not improbably the 

 true dolphin was an immediate contemporary. The baleen whales 

 proper are not known before the Pliocene, when, in addition to 

 Balaana, and possibly Neobaljena, we meet with a number of extinct 

 types more or less closely related to these — Balaanula, Idiocetus, 

 Plesiocetus. Balffinotus, from the Antwerp Crag, is a connecting 

 form between the baleen whales and the rorquals, and Bartinop- 

 sis between the rorquals and humpbacks. Cetacean remains are 

 abundant in the Post-Pliocene deposits, and comprise a variety of 

 recent types ; the narwhal has been indicated from the deposits of 

 England and Siberia. The Miocene deposits of the Eastern United 

 States have yielded a number of delphinoid remains to which the 

 generic names Priscodelphinus, Tretosphys, Zarachis, Lophocetus, 

 Rhabdosteus, and Ixacanthus have been applied. 



Insectivora. — The animals of this order, which comprises barely 

 more than one hundred and thirty to one hundred and forty living 

 species, of which about one-half are true shrews (Soricidae), are 

 distributed over the greater part of the earth's surface, but are 

 absent from both South America and Australia. The greater num- 

 ber of the nine generally recognised families are limited to com- 

 paratively narrowly circumscribed distributional areas, which in 

 some cases are only co-extensive with the sub-regions or provinces 

 of the main zoogeographical divisions. The GaleopithecidsB, or 

 flying-lemurs, which were formerly referred to the true lemurs, 

 and by some naturalists to the bats, are the most aberrant forms of 

 the order, and constitute the type of a distinct sub-order, Insecti- 

 vora dermoptera. But two species are known, Galeopithecus volans 

 and G. Philippinensis — the former an inhabitant of the forests of 

 the Malay Peninsula, Sumatra, and Borneo, and the latter of the 

 similar districts of the Philippine Islands. The squirrel- or tree- 

 shrews (Tupaiidse), small arboreal insectivores resembling squirrels 

 in outline and habits, are restricted to the Oriental region, where 

 they range from the Khasia Hills, in India, to Java and Borneo. 

 Of the two genera, Tupaia and Ptiloccrcus, tlie latter contains but 



