European Species of (he Subgenus Pity my?. 513 



represented in the Natural History Museum by fourteen 

 speeimens collected at Ciutra by Mrs. Mary and !\lr. Oldfield 

 Thomas. Mrs. Thomas not only assists her husband during 

 liis collecting-trips, but science is further indebted to her for 

 helping in the arrangement of the collections of skulls of 

 small mauimals in tlie Natural History ^luseum ; I have 

 therefore associated her name with the species fioni (ialicia 

 described further on. 



Microtus lusitunicus belongs to the same group as M. duo- 

 decimco status, as revealed by the arched upper contour of 

 its skull, its deep, subcylindrical brain-case, the backward 

 shelving of its occipital, its protruding ui)per incisors, and 

 the absence of closed triangles in nt" , the middle outer 

 triangle of which is much reduced. The characters of the 

 skull and of the incisors are somewhat less pronounced 

 than in the larger species of the group. Those of nv" con- 

 versely are very well marked : out of the fourteen speeimens 

 only in three is the reduction of the middle triangle not so 

 marked as usual — in one (no. 98. 2. 2. 49) this occurs on 

 both sides, in two (nos. 98. 2. 2. 41 and 47) on the right side 

 only. The fusion of the two middle (outer and inner) 

 triangles, leading to the formation of a transverse loop and 

 consequently to the absence of any closed triangle in this 

 tooth, is constant in all the fourteen speeimens. 



The development of a supplemental triangle on m-, more 

 rarely on w} also, which is a characteristic feature in adult 

 specimens of several species of the subgenus, is of rather 

 exceptional occurrence iu the members of the duodtcim- 

 costatus group. Out of the fourteen specimens of the present 

 species only two exhibit this pentamerodont character. In 

 one (no. 98. 2. 2. 37) the supplemental triangle is moderately 

 developed on both the m', in the other (no. 98. 2. 2. 47) it is 

 more conspicuous and a beginning of a similar development 

 is visil)le also on the right m^. 



Coloration. — Above "bistre'^"^, some specimens approaching 

 more to " broccoli-brown.^^ The bistre-coloui'ed are 

 " smoke-grey " below, with a more or less admixture of 

 "bufi" in those approaching to "broccoli-brown^' in the 

 up[)er parts. (All the specimens from Cintra are of a 

 decidedly darker coloration above than that exhibited in 

 another species of the M. duudechncostatus group froni the 

 neighbourhood of ISeville. The largest of these, represented 

 by immerous specimens in the Natural History Museum, 



* For names of colouis placed iu inverted commas see K. Kidgwaj', 

 'A Nomenclature of Colors for Naturalists ' (Boston, 1886). 



