1895.] ^' [Slade. 



projecting process. The dental series in this suborder resembles that of 

 the Insectivora, the molars being cuspid. Adopting the classification of 

 the highest authorities, and notably that of Dr. Dobson, the Insectivora 

 may be divided into two suborders, the Dermoptera and the Insectivora 

 Vera. Accepting the above classification, the Insectivora, so far as con- 

 cerns the jugal arch, may be brought into three groups : 



1. Those in which the arch is complete and well developed, comprising 

 the Tupaidaj, Macroscelidae, Rhynchocyonidae, Galeopithecidse. 



2. Those in which the arch is complete but more or less feebly devel- 

 oped, comprising the Erinaceidoe, Talpidse, Chrysochloridse. 



3. Those in which the arch is partially or wholly deficient, comprising 

 the Centetidfe, Potamogalidse, Solenodoutidos, Soricidse. 



The Tupaia may be taken as a typical form of the first group. The 

 jugal arch is well developed, a postorbital process from the frontal meet- 

 ing a corresponding one from the malar, thus forming a complete bony 

 orbital ring. The malar has a large longitudinal oval vacuity, which, 

 although unique in this case, when taken with similar vacuities in the pal- 

 ate of this genus, as also In some of the other Insectivora, points unmis- 

 takably to the Marsupialia. 



The horizontal curvature of the arch is sufficient to counteract any 

 inherent weakness due to the vertical curvature with its convexity down- 

 wards. The temporal fossa is moderately extended, while the coronoid 

 surface of the mandible presents a large backward projecting surface, ris- 

 ing high above the transversely produced condyle. 



In the second group, where the arch, although complete, is for the most 

 part weak, the cranium presents marked modifications. In Erinaceus and 

 Gymnura the arch is formed mostly by the processes of the squamosal and 

 maxilla which join, while the malar is very small and occupies in a splint- 

 like form the outer and under sides of the centre of the arch. There are 

 no traces of any postorbital processes. The temporal fossa is deep and 

 extended, while additional surface is afforded for the temporal muscle by 

 the prominence of the sagittal and occipital crests. The ascending ramus 

 of the mandible, with its broad, concave, coronoid surface, and the devel- 

 opment of the pterygoid fossse, denote increased masticatory powers, in 

 spite of the apparent weakness of the buttress. 



In the Talpidse, certainly in all of the truly fossorial of the family, the 

 jugal arch is slender, and exhibits no distinct malar bone, no occipital or 

 sagittal crests, and no postorbital processes. 



The mandible is long, and the vertical portion presents a moderately 

 extended coronoid surface with a small transverse condyle. The infra- 

 orbital foramen is of great size, being a very slender osseous arch which 

 serves for the transmission of the large intraorbital branch of the trifa- 

 cial, affording the necessary svipply of sensory nerves to the muzzle. 



In the Chrysochloridse, which in the general shape of the skull present 

 modifications different from all other Insectivora, the jugal arch is in some 

 species so expanded vertically, that, as Dr. Dobson remarks, "their upper 



TROC. AMEK. PHILOS. 80C. XXXIV. 147. H. PRINTED MAY 8, 1895. 



