RATTUS : 733 
(a) Size large (head and body to 112, hind-foot to 25 mm.); dorsal 
colour not rufous. 
(@) Skull slightly smaller (condylo-basal 
length to 24.7 mm.), ridges feeble, 
brain-case smoothly rounded anteriorly. 
(a”) Ventral surface dark, pectoral spot 
often lengthened into a median 
longitudinal thoracic and abdominal 
streak. . : : ‘ : . hebridensis hebridensis 
(Lewis). 
(2°) Ventral surface silvery, pectoral spot 
absent or feebly developed. . . hebridensis maclean 
(Mull). 
(61) Skull larger (condylo-basal length to 
25.5 mm.), ridges comparatively strong, 
brain-case angular anteriorly. Belly 
silvery ; pectoral spot evident. : . hebridensts hamiltont 
(Rum). 
(4) Size smaller (head and body to 95, hind- 
foot to 23 mm.). General dorsal colour 
rufous. Belly silvery ; pectoral spot scarcely 
developed. : : : : : . hebridensts cumbrae 
(Great Cumbrae). 
GENUS RATTUS (= pzmys). 
On p. 575, e¢ seg., Epimys Trouessart is used as the generic 
name of the true rats. Hollister (Proc. Bzol. Soc., Washington, 
1916, 29, p. 124) has pointed out, however, that Fischer in 
1803 (Das Natronal Museum der Naturgeschichte zu Paris, 
Bd. 2, p. 128) used Rattus (misprinted Ruttus) for this 
purpose validly. The name Aattus must therefore supersede 
Epimys, a regrettable though quite unavoidable change. 
Hollister thought that decumanus (i.e., norvegicus, was the type 
species of Fischer’s genus Rattus; but Thomas (dxzn. Mag. 
Nat. Hist., 18, p. 240), and Hinton (/ourn. Bombay Nat. 
Fist. Soc., 23, p. 59) agree that Fischer took vattws and not 
norvegicus as the genotype. The correct technical names 
of the species occurring in Britain are now therefore :— 
1. Rattus rattus, with its sub-species 7 vattus, r. alex- 
andrinus, and r. frugivorus. 
2. Rattus norvegicus. 
