DESCRIPTIONS OF GENERA AND SPECIES. 193 



of botli descriptions in the genus Qlycyphagus, but that 

 is a very specialised and varying genus, which may 

 have to be divided some day, although it is difficult to 

 see how it can be satisfactorily done at present, without 

 further knowledge of some of the forms. The demar- 

 cation is quite as strong in the young of Lentungula as 

 in the adults. It may, of course, be said that Megnin 

 had only a small number of specimens, which had 

 been kept in some preservative liquid ; but even under 

 these disadvantages I cannot think that so careful an 

 observer as Megnin would have missed so important a 

 character. 



As far as I know the genus Lentungula has been 

 adopted by all writers up to this time who have dealt 

 with the subject. 



Tyroglyphidae with the ambulacrum of each of the 

 first two pairs of legs consisting of a minute mono- 

 dactile claw only, without sucker or caroncle ; this claw 

 is borne upon a long flexible peduncle arising from the 

 side of the tarsus. It can be flexed at the will of the 

 creature. Ambulacra of the two hind pairs of legs 

 large, monodactile, sessile claws; without suckers or 

 caruncles. Mandibles chelate. Cephalothorax and 

 abdomen clearly divided from one another. Without 

 marked sexual dimorphism. 



This is a wholly exceptional genus of Tyroglyphidse ; 

 subject to what is said above relative to Megnin's 

 Hyadesia. Firstly, it is the only genus of the family 

 which is aquatic, or semi-aquatic; although certain 

 others, as Herioia, Histiostoma, etc., are usually found 

 wading in vegetable juices. Secondly, it is one of the 

 very few genera of Acari, outside the Halicaridse, 

 which has any claim to be considered marine ; the two 

 species of this genus known are inhabitants of salt or 

 brackish water. They are not, however, swimming 

 creatures; they are strictly and solely crawlers, fre- 

 quenting algge and stones in shallow water, or even left 



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