THE FOULA FIELD MOUSE 729 
each of the other sub-species of /rzdarienszs, but its angular process 
shows no trace of the remarkable elongation characteristic of f. grantit. 
These appearances are borne out by the measurements, which in 
addition reveal some small peculiarities of the present form. The 
absolute size of the skull is about as in f grantiz, the occipito-nasal 
length, interorbital width, nasal length and width, and the length of the 
anterior palatal foramina, are dimensions which tend to be smaller 
relatively than in the other sub-species of frzdariensis; while the 
zygomatic breadth, cranial width, and post-molar length tend to increase 
in relative value. The rostrum is relatively wider than in f fridarzensvs, 
narrower than inf. granti ; the masseteric plate is relatively narrower 
than in f# grantd, much narrower than in true /7zdartensis ; the length 
of the tooth-row is nearly as in f fridariens?s, distinctly shorter relatively 
than in f. grantiz. 
DIMENSIONS IN MILLIMETRES :— 















i) 3 3 a 
FI mb 3 a mb < 3 
No. Date. o| 3 |= | & i No. Date. eee |p | ae 
23/8/28 |8 g3(e|/2 | 8 
ie] isl jes] 3] 
MALEs. FEMALES. 
Skins— Skins— 
1 Oct. 1917 96 24-2 | 16 5 Nov. 1917 (Type)| 101°5 | 102 26 
4 Noy. 1917 95 94 26°5) || «6 6 Nov. 1917 93°5| 90°5| 24°7 
% Nov. 1917 87°5| 92 26 = |(juv.) 8 Noy. 1917 103°5| 88 PE ANE a8 
9 Dec. 1917 97 91 25 15 B Nov. 1917 98 98 25 16 
11 Dec. 1917 100 93 26 15°5 10 Dec. 1917 104 94°5| 25°3) 15°5 
12 Dec. 1917 98 96 25°5 | 15°5 13 Dec 1917 91 92 25 14 
15 Dec. 1917 90 68°5| 25 15°5 14 Dec. 1917 90 90 25 14 
In Spirtt— In Spirit— 
9th April 1917 89 92 23 15 April 1917 81 82 23 15 
9th April 1917 86 97 24 15°5 April 1917 86 83 24 15 
9th April 1917 77 83 23°5 | 16 April 1917 96 95 23°5] 16 
9th April 1917 84 96 25 15 Novy. 1917 80 81 23-5] 14 
9th April 1917 83 78 | 24 15 Noy. 1917 77 77 23 13°5 
Noy. 1917 "82 82 23 16°5 Nov. 1917 82 81 225) 13°5 
Nov. 1917 86 92 25 15 Nov. 1917 81 86 24 16 
Noy. 1917 85 84 24 15 Nov. 1917 91 98 24 16 
Jan.-Feb. 1918 94 ne 25 15°5 Nov. 1917 87 an 24 14°5 
Jan.-Feb, 1918 86 87 28°5 | 16 Jan.-Feb. 1918 90 94 24 16 
Mar.-Ap. 1918 98 95 24°5 | 16°5 
Mar.-Ap. 1918 88 95 23°5 | 15 
Skeleton— 
2 Oct. 1917 101 ae 25°2 | 16 
Average of 20 90 90°2| 24°5 |) 15-4 Average of 17 90 89°5| 24:2) 14°9 
COMPARISON OF EXTERNAL MEASUREMENTS. 
Absolute (in millimetres). Relative (head and body = 100). 

A. fridariensis thulco 
Average of 9adult males . ° 96°5 98 25:1 15°7 100 96°5 261 16°3 
Average of 10 adult females 4 95°8 94°2 24-7 15'3 100 98°5 26°8 16 
A, fridariensis fridariensis 
AverageofGadults . Py + | 109°5 106°2 241 16°1 100 94 22 147 
A. fridartensis grantit 
Average of 10 adults . 3 + | 101°5 91°8 24 16°2 100 90 23°6 16°9 

VOL, II. 3A 
