CREUSIA SP1NUL0SA. 881 



cation or union of the scuta and terga ; but we have seen this is a point 

 which is variable in Elminius Kingii, Pyrgoma milleporce, and in some 

 species of Balanus. The serial affinities, moreover, in Pyrgoma, clearly 

 show that this is a character of no great importance. I must add that 

 in several specimens of several of the varieties, the scuta and terga 

 were so closely joined, that until careful examination, I was unable to 

 detect the suture separating them ; such being the case it must be 

 quite unimportant for any functional purpose, whether or not the 

 valves are calcified together. I feel, consequently, hardly any doubt 

 that I have acted right in treating the present form as a mere variety. 

 Var. (10) an. spec.1 fig. 6t. — Hab. Unknown. — This variety bears 

 nearly the same relation to var. 6, as the last variety did to var. 3. The 

 shell is rather stronger than in var. 6, with the internal ribs not so 

 prominent ; and except in being tinted pale dull purple, it differs in 

 no respect from the shell of var. 1. If we imagine the scutum and ter- 

 gum in the third sub-variety of var. 6 (6 p, 6 q), in which the adductor 

 ridge descends far beneath the true basal margin of the valve, to be calci- 

 fied together, without any suture, we shall produce almost the identical 

 valves of the present variety. The scutum, however, here is not quite 

 so much elongated transversely, and the occludent margin is spinose 

 and is furnished with large teeth ; these two characters give the valve 

 a somewhat different aspect, and hence I am more doubtful than in the 

 foregoing case, whether this form may not be specifically distinct. I 

 must, however, state that in Tetraclita porosa, I ascertained that the 

 teeth on the occludent margin of the scuta were even more variable 

 than here is supposed to be the case ; and as for the shape of the 

 valve we have seen what wonderful variation there is in var. 6. The 

 tergum in this variety is about intermediate between the two common 

 forms, in the sub -varieties of var. 6. As for the calcification of the 

 two valves together, we have seen, under the last variety, how little 

 important a character it is. 



Far. (11) fig. 6u, 6u [Creusia grandis, of Chenu, Tab. 1, fig. 2, 

 but not fig. 2 a and b]. — Hab. Singapore, associated with Pyrgoma 

 monticularice. — This variety is very closely related to the last. The shell, 

 however, has a very peculiar aspect, which made me for some time 

 think it must be specifically distinct. It is of a much brighter pink 

 than in any of the foregoing varieties ; the surface is marked with very 

 prominent, distant ribs, and the radii are narrow, in which latter points, 

 together with the tint (though here brighter), this variety cannot be 

 distinguished from var. 7. The shell, however, is permeated by several 

 rows of pores, in which respect it resembles the shell in var. 2, and 

 some specimens of vars. 3 and 4. In the opercular valves there is a 

 close general resemblance with those of the last var. 10; the tooth, 

 however, near the rostral angle, is not so prominent ; and in the tergum, 

 the spur is more truncated, shorter and broader than in var. 10, and 

 closelv resembles that in var. 1 and 2. But I cannot consider anv of 

 the points here specified of much weight. 



The foregoing descriptions show how singularly the affinities of the 

 several varieties interlock in the most complicated manner. Hereafter 



