CONGHODERMA VIRGATA. 151 



the carina had its usual outline, as had nearly the scutum 

 on one side, whereas, on the other side, it presented a 

 new and peculiar form, having five ridges or points, and 

 was imperfectly calcified ; seeing this, it was impossible 

 to place much weight in the precise form or size (and 

 therefore, relative separation,) of the calcified valves ; and 

 on close examination, I found every part of the mouth 

 and cirri identical in Leach's Cineras chelonophilus and 

 C. Olfersii, and in the common form. Therefore, I con- 

 clude, that C. chelonophilus, and still more C. Olfersii, 

 are only varieties ; the terga presenting the greatest, yet 

 variable, amount of difference, namely, in their acumina- 

 tion and flatness. We know, also, that in the species 

 of the closely allied genus of Lepas, the terga are very 

 variable in shape, and this is the case, even in a still 

 more marked degree, in Conchoderma aurita. Professor 

 Macgillivray, 1 may add, has come to a similar conclusion 

 regarding the extreme variability of the valves of this 

 species. 



As the varieties here mentioned are very remarkable, 

 and may perhaps turn out to be true species, I think they 

 are worth describing in some detail : I will only further 

 add, that we must either make several new species, or 

 consider, as I have done, several forms as mere varieties. 



C. virgata, var. chelonophilus of Leach. PI. Ill, fig. 2 c. 



Atlantic Ocean, 35° 15' N., 16° 32' W. On the Testudo caretta. 



Capitulum not above half an inch long, composed of very 

 thin membrane, with six bands (as stated by Leach) of 

 faint colour; summit bluntly pointed; valves very small, 

 far distant from each other ; the scuta are imperfectly cal- 

 cified, the central part of the umbo consisting of thick, 

 brown chitine, with imbedded shelly beads ; terga and 

 carina perfectly calcified. 



Scuta trilobed, flat, within slightly concave, upper lobe 



