406 
PROF. B. T. LOWNE OFT THE 
each tarsus, besides a few others. The penis is placed on the 
ventral surface in the median line between the hinder part of the 
coxte of the third legs ; the vulva between those of the second 
legs. 
I found the creature on the surface of, or very slightly buried 
in, a depression of the skin lining the inner side of the external ear 
of the short-tailed, field-vole ( Arvicola agrestis ). I believe it to be 
unrecorded, and propose to call it “ Goniomerus musculinus 
DESCRIPTION OP PLATE XXVI. 
Fig. 1. 
Myocoptes tenax , $ . 
Dorsal aspect. X 175. Drawn 
specimen with long abdomen. 
from a 
2. 
ff if if 
Ventral aspect. X 175. Drawn 
specimen with short abdomen. 
from a 
3. 
if if if 
From the side. X 175. Natural position, 
holding the hairs of the mouse. 
4. 
ff f? <$ • 
Dorsal aspect. X 175. 
5. 
„ » ff 
Ventral aspect. X 175. 
6. 
,, „ nymph. Dorsal aspect. 
7. 
» $• 
3rd leg, seen from the inner side. 
X 350. 
8. 
Symbiotes tripilis, . 
Ventral aspect. X 130. 
9. Goniomerus musculinus, J . Dorsal aspect. X 175. (There is 
another pair of long hairs on the hind margin, below and 
hidden by the pair shown.) 
On the Structure of the Retina of the Blowfly ( CallipJiora ery- 
fhrocephala). By Benjamin Thompson Lowne, R.R.C.S., 
F.L.S., Hunterian Professor of Comparative Anatomy in 
the Royal College of Surgeons. 
[Read 21st February, 1889.] 
(Plate XXVII.) 
In 1S84 I had the honour of reading a paper before this Society 
on the compound vision and morphology of the eye in insects, 
which was published in the second volume of the new series of 
‘ Transactions.’ 
That paper received at the time much adverse criticism, and 
Dr. Hickson published a memoir in the £ Quarterly Journal of 
Microscopical Science,’ in which he convinced himself that he had 
completely refuted my observations. 
