200 BRITISH TYROGLYPHID^. 



plate covers the longish curved penis (fig. 10) and the 

 somewhat elaborate skeleton which supports it (fig. 9). 

 This consists of a horseshoe-shaped sclerite, with thick, 

 projecting, posterior ends joined by a broad band ; 

 from a central projection of which the penis arises. 

 The anterior end of the organ, when at rest, is sup- 

 ported by a notch formed by two short rods attached 

 to triangular blade-like sclerites on edge. 



Habitat. I found a large number of specimens in a 

 patch of green alga (Cladophora fracta), growing 

 where the fresh water of a small stream trickled over 

 the face of the granite cliffs within reach of the spray 

 of the sea, near the Land's End, Cornwall. I have 

 not found it elsewhere, and I am not aware of anyone 

 else having done so. 



SUB-FAMILY Histiostomidse. 



The characters of the sub-family are necessarily 

 those of the only genus contained in it, viz. Histio- 

 stoma. 



GENUS HISTIOSTOMA * (Kramer). 



Histiostoma, 1876. Kramer, " Beitrage zur Naturgeschichte der 

 Milben," in 'Arch. Naturg.,' 42 Jahrg., 

 Heft 1, p. 105. 1889, ' Thierreich,' Lief. 7, p. 

 133. 



1888. Oanestrini, ' I Tiro,' p. 5 ; Pros., p. 354. 

 1895. Jensen, "En Tyroglyphide i Hesteiglens (Eg 



Kapsel," in ' Vid. Medd.' (Copenhagen), 

 January, 1895, pp. 72104. 

 1896. Berlese, 'A.M. S.,' fasc. Ixxix, No. 6. 



Phyllostoma,-f 1876. Kramer, " Beitrage zur Naturgeschichte der 

 Milben," in 'Arch. Naturg.,' 42 Jahrg., 

 Hft. 1, p. 39. 



Serrator, 1880. Megnin, ' Les Parasites,' p. 145. 

 Hypopus,l 1883 to 1887. Berlese, 'A. M. S.,' fasc. ix, Nos. 7 and 8 ; 



fasc. xxix, No. 4 ; fasc. xxxix, No. 9 ; 

 Notes, fasc. i, p. 14. 



'* 'IO-T'IOV, a sail, tissue, or web; Gropa, the mouth. 



f Name preoccupied by Geoft'roy and Cuvier, 1797, Chiroptera: E. 

 Geoffroy, St.-Hilaire, 1870. 



% Sednon Hypopus, Duges, 1834, 'Ann. Sci. Nat.,' ser. 2, vol. i, p. 

 37, which was simply the hypopial stage of any of the Tyroglyphida3. 



