Vol, 5. p. 369-382, pi. 19. August 10, 1931. 



Occasional Papers 



OF THE 



Boston Society of Natural History. 



A COMMON ARBOREAL MOSS MITE 

 H UMEROBA TES H UMERA LIS. 



BY ARTHUR PAUL JACOT. 



Since this arboreal acarian of the family Oribatidae has not 

 previously been recorded from New England, though common, 

 and since it has never been properly figured nor its external mor- 

 phology been fully appreciated, the present contribution has 

 been prepared. 



Description. — Cephaloprothorax as seen from above (PI. 19, 

 fig. a, b, d-f) short, conical, with convex sides, outline broken by 

 rostro-lamellar ridges and tectopedia I, the latter forming very 

 prominent lateral horns if viewed from somewhat in front (PI. 

 19, fig. a); seen from side (PL 19, fig. b), semiconical, slightly 

 undulate, with somewhat protuberant rostrum; lamellae slender 

 blades of subequal diameter throughout, slightly undulate on 

 lateral edge, with well-defined, basal channel; apex free, truncate 

 (PL 19, fig. b, d-f) to slightly emarginate to receive the bristle; 

 restro-lamella ridge undulate, springing from median edge of 

 lamellae, converging, terminating close beside rostrum, distant 

 from lamellar bristles. I should here point out that the rostro- 

 lamellar ridge in Scheloribates diverges to rostral bristles, so that 

 it is a parallel phenomenon without direct phylogenic relations. 

 So prominent are these ridges as to form two prominent nubbins 

 on each side of rostrum tip even when viewed from below (PL 

 19, fig. a), though this is partly due to their being produced 

 ventrad of camerostome rim! (PL 19, fig. b, d, /); translamella 

 not developed, but apex of lamellae with a median truss which has 

 the appearance of a rudimentary or fragmentary translamella; 

 bristles long, slightly hispid, rostral bristle almost ciliate in some, 

 inserted at juncture of distal end of tectopedia I and side of 

 cephaloprothorax, interlamellar inserted very close to rim of 

 notogaster; tectopedia I slender, cuneate blades, longitudinally 



369 



