GEORGE HODGE ON NEW MARINE ACARI. 299 
Mr. Gosse, in the paper before alluded to, mentions the dif- 
ference he observed between two specimens of Halacarus ctenopus. 
One appeared destitute of eyes, for he says, ‘No eyes were 
visible, unless a black speck on each side of the bulb of the 
rostrum was an eye, which I much doubt, from the position of 
the conspicuous organs of vision in the former species,” (H. 
rhodostigma). The next he examined had three eyes. ‘Strongly 
conspicuous, also, were two lateral black eyes, which exactly 
agreed with those of H. rhodostigma, and a third orbicular eye, 
also black, close behind the rostrum. Neither of these eyes was 
visible in the specimen I before examined.” And as the number 
and position of the eyes vary, so do their form and size. In 
Pachygnathus, the visual organ consists of a single, highly 
refractive dark coloured sphere. In Halacarus, they take an 
irregular form, slightly angular, and apparently composed of a 
number of minute, dark-coloured granules, aggregated together, 
and so minute that they cannot be separately resolved. In 
Leptognathus, the lateral eyes are a mulberry-like mass, con- 
sisting of about eight moderately large spheres closely associated ; 
the central anterior organ, consisting of four such spheres, 
smaller than the lateral ones, and of irregular size, differing in 
this respect from the others, which are moderately uniform in 
dimensions. These spherules are very minute, the largest being 
sooo Of an inch in diameter, and the smallest half that size, 
ea 
OY z000° 
Crass. ARACHNIDA. 
Orprer. ACARINA. 
Famiry. ORIBATAD A. 
Genus. HALACARUS, Gosse. 
1. A. granunatus. Pl. XVL, figs. 4, 5. 
Length of body to tip of rostrum, g5 of an inch; colour, 
orange brown; legs, searcely coloured ; the shield trun- 
cate a little below the insertion of the palpi. 
Rostrum tapering to a short point, and furnished with two 
long mandibular organs, with a jointed process at their 
free ends. Palpus composed of four joints, the second 
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