482 BALAN1D/K. 



15. Genus — Octomeris. PL 20. 



Octomeris. G. B. Sowerby. Zoological Journal, vol. 2, p. 244, 

 July, 1825. 



Compartments eight: radii with their edges crenated: 

 basis membranous. 



Distribution, Cape of Good Hope ; Philippine Archipelago. 



The two species of this genus differ considerably in 

 external appearance, though not in essential character. 

 Both, as the name expresses, have eight compartments : the 

 carino-lateral pair are rather narrower than the lateral. The 

 basis is membranous. The radii are narrow, and are dis- 

 tinctly crenated on both sides of the sutures with the teeth 

 neatly interlocking ; but these teeth can hardly be distin- 

 guished in the large, corroded specimens of 0. angidosa. 

 The crenated structure of the radii is identical with that 

 described under Chthamalus dentatus and Hembeli; if, 

 indeed, we were to add carino-lateral compartments to 

 the shells of these two species, they would belong to Octo- 

 meris. I have seen only a few specimens of either species 

 of Octomeris, and none preserved in spirits ; and there- 

 fore I know nothing of the anatomy of the softer parts: 

 I was not able to make out distinctly any branchiae. The 

 cirri differ considerably in the two species, in nearly the 

 same way as in the two species of Chamsesipho. In the 

 structure of the second pair of cirri, and in the tendency of the 

 basal margin of the parietes to form bay-like indentations, 

 Octomeris angulosa shows some special affinity to Chamcesipho 

 scutelliformis. Under Pachylasma, I stated that that genus 

 was closely related to Octomeris ; and 1 have just alluded to 

 the close affinity of the latter to the division of the genus 

 Chthamalus, which has crenated radii. 



