298 GEORGE HODGE ON NEW MARINE ACARI. 
XX XVITI— Contributions to the Marine Zoology of Seaham 
Harbour. By Guoree Hoper. (Pl. XVI. fig. 4—11.) 
On some undescribed Marine Acari. 
Little attention has been paid to the British species of marine 
acari, judging from the few species at present known. No doubt 
their rarity and minuteness have been the principal reasons for 
this apparent neglect; for, with the exception of Professor 
Allman and Mr. Gosse, no naturalists have recorded their 
capture in our seas. The former discovered a single species in 
the nostrils of a seal, as mentioned by Mr. Gosse, who describes 
three species,* viz., Halacarus rhodostigma, H. ctenopus, and 
Pachygnathus notops, found by him amongst sea-weed, the two 
former at Weymouth and the latter at Ilfracombe. I figured a 
species of the latter genust (P. Seahami), which is found here 
amongst sea-weed ; and, to the best of my knowledge, these are 
the only recorded British species. 
A careful search, during the last two years, amongst the 
refuse washed from zoophytes, &c., from deep water (15-25 
fathoms), and from between tide marks, has rewarded me with 
four forms, which I take to be new. Two of them evidently 
belong to the genus Halacarus, one to Pachygnathus, and the 
other to Leptognathus. 
Before proceeding to describe these animals, it may not be 
amiss to allude to the extraordinary difference in the number 
and position of the visual organs. In one species these organs 
are altogether absent (Halarachne halicheri) ; im another we 
find a single dark eye just behind the base of the rostrum 
(Pachygnathus notops); im another a dark irregular patch at each 
side of the thorax, at the base of the second legs, (Halacarus 
oculatus ); in another, two compound eyes similarly placed to the 
last, with the addition of a much smaller compound eye, just 
behind the rostrum (Leptognathus falcatus ). 
* Annals and Magazine of Natural History, 1855, vol. 16. 
+ Transactions of Tyneside Naturalists’ Field Club, vol. 4, page 319. 
