70 Memoirs of the Indian Musemn. ' [Voi,. II, 



occludent margin considerably thickened ; the carinal margin straight or slightly 

 convex ; the scutal margin almost straight. Scutum subtriangular, its lower part 

 inflated ; the occludent margin more or less convex ; the carinal margin straight or 

 convex backwards , the basal margin almost straight ; the umbo nearer the base of 

 the occludent margin of the valve than the apical angle, which is more or less 

 produced; a prominent ridge, which runs down the occludent margin, and a deep 

 impression for the adductor muscle, present on the inner surface of the valve. Carina 

 very broad, elbowed, the basal branch about half as long as the vertical one; the 

 external surface tuberculate, the internal surface smooth, with a deep vertical groove; 

 the base expanded into a small transversely oval or subquadrangular, flat disk. 



Peduncle short, cylindrical, irregularly annulated, very hard and stiff, covered 

 with chitinous spines. 



Cirri, etc. — All the cirri long and curved, the rami of the second pair subequal, 

 about three times as long as the pedicel. First pair not widely separated from the 

 second; rami slender, subequal, with about ii joints, the anterior face of each 

 joint covered with transverse rows of bristles with distinct circular sockets ; the distal 

 joint ending in two very long bristles with several shorter hairs. Anal appendages 

 reduced to mere minute prominences bearing five or six long, delicate hairs. Penis 

 long, slender, pointed, bearing scattered hairs ; the distal half annulated and ridged 

 longitudinally ; the whole organ densely pigmented except for a comparatively large 

 area near the base. 



Fig. I. — Labnim of 0. celata sub-sp. indica, viewed from the left side. 



Mouth parts. — Labrum produced into an oval, concave, somewhat spatulate plate, 

 which is relatively broad when seen from above but appears cylindrical and horn-like 

 when viewed from the side; it is almost twice the length of the palpi. Pa'pi stout, 

 bluntly pointed, bearing a fringe of rather long, deHcate hairs at their tip. Outer max- 

 illa broadly oval, subtruncate, bearing an irregular fringe of hairs of different lengths 

 which is best developed on the anterior border. Maxilla narrow; its cutting edge 

 with an excavation near the outer margin and with the inner part very prominent ; 

 external to the excavation one large bristle and on either side of it {i.e., on either face 



