410 CEYLON PEARL OYSTER REPORT. 



Trapezia cymodoce (Heebst, 1801) A.3, p. 219. 



Localities: Muttuvaratu Paar, four specimens (e,f, g, h); Jokkenpiddi Paar, one 

 specimen (k) ; coral reef, Galle, twelve specimens (m, n, p, q, r, s, t, u, v, w, x, y) ; 

 pearl banks, Gulf of Manaar, eight specimens {a, b, c, d, i,j, k, o). 



Description : Alcock's observation, that the carapace of the adult female is more 

 curved than that of the male, is reversed in the present series. Variation concerns-- 

 (1) size : the size of adult specimens varies a good deal, e.g., two adult males C.l. = 6'25 

 and 16-0, and two ovigerous females C.l. = 575 and 1075; (2) the outer angles of 

 the frontal lobes : these are entire in most, but crenulate in adult male (*") and in 

 ovigerous female (b), and they tend to be so also in (j) young ? , (m) ovigerous ? , and 

 (n) adult S ; (3) the outer orbital angle is in most cases produced and pointed, 

 but in the adult male (k) and also in (p), (</), and (r) it is blunt, in ovigerous ? 

 (v), ovigerous ? (x), and adult S (y) it is only slightly produced, and in adult 

 <$ (w) it is not produced ; (4) the lateral epibranchial spine is quite obvious and sharp 

 in most cases, but in (k), (p), (q), and (r) it is blunt, while in (v), (.r), and (y) it is 

 obsolescent. It will be noted that variation of outer orbital angle and of lateral 

 epibranchial spine are correlated. 



A specimen (z) from " Lagoon, Galle, 1903," may be conveniently included here as 

 a variety. In it the lateral epibranchial tooth of the carapace is absent, the antero- 

 lateral borders diverging posteriorly to form a continuous curve with the anteriorly 

 divergent postero-lateral borders. The hand is naked. The front agrees fairly with 

 that of T. ferruginea or T. cymodoce. I would name it var. edentula. 



Another specimen (z"), a doubtfully mature male, has the merest trace of a lateral 

 epibranchial tooth and a rather strongly reflected front. 



Remarks. The specimens (p), (q), and (r) combine the outer orbital angle, the 

 lateral epibranchial tooth, and the inner sub-orbital tooth of ferruginea with the 

 hand of cymodoce. The front is intermediate in character. The specific distinction 

 between the two species is thus minimised. Judging from my specimens and from 

 those in the British Museum, the best distinction is the hair of the hand. 



Trapezia ferruginea, Latreille, var. areolata, Dana, 1852 A.3, p. 221. 



Localities : Coral reef, Galle, two specimens ; Trincomalee, one specimen ; Cheval 

 Paar, two specimens ; Jokkenpiddi Paar, two specimens. 

 Description: C.l. of an ovigerous female = 12. 



Trapezia maculata (Macleay, 1838) A.3, p. 221. 

 Locality : Jokkenpiddi Paar, two specimens (young c? and young ? ). 



Trapezia rufopunctata (Herbst, 1799) A.3, p. 222. 



Locality : Jokkenpiddi Paar, one specimen. 

 Description; An ovigerous female, C.l. = 13, 



