354 balanidjE. 



narrow, and are quite smooth-edged, differently from in E. plicatus. 

 The edges of the aire barely exhibit a trace of being crenated. 



In the body I could perceive no difference from E. plicatus, ex- 

 cepting that in the third pair of cirri the two rami are like each other, 

 and do not support any coarsely pectinated, only serrated, spines ; but 

 after what we have seen on the variability of these very same characters 

 in Tetraclita porosa, I dare not trust to them. The three posterior 

 pairs of cirri, also, seem here to be more elongated in proportion to 

 the others, than in E. plicatus. 



Affinities. — It is certain that this species is most closely allied to 

 E. plicatus ; but as I have seen many specimens of the latter brought 

 by different persons from New Zealand, and as I have observed in them 

 no approach to the characters of E. simplex, which, in specimens from 

 three localities, also appear to be constant, I have considered the two 

 forms as specifically distinct. The present species differs from E. pli- 

 catus, in its white, conical, moderately ribbed, well preserved, smaller 

 shell ; and more especially in the orange-coloured intermediate lamina 

 of E. plicatus being here represented only by microscopically minute 

 dots. But the radii being smooth-edged, is the most important differ- 

 ential character, though in E. plicatus, during its earliest growth, 

 whilst still immature and colourless, the radii are likewise smooth- 

 edged. 



5. Genus — Pyrgoma. 



Pyrgoma. Leach. Journal de Physique, torn. 85, 1817. 

 Boscia. Ferussac. Diet. Classique d'Hist. Naturelle, 1822. 

 Savignium. Leach. Zoological Journal, vol. 2, July, 1825. 

 Megatreha. Lb. lb. 



Adna. Lb. lb. 



Daracia. /. E. Gray. Annals of Phil, (new series), August, 1S25. 

 Creusia. Be Blainville. Diet. Sc Nat., PL 116, 1S1G-30. 

 Nobia. G. B. Sowerby, junr. Conchological Manual,* 1839. 



Shell formed of a single piece ; basis cup-formed, or sub- 

 cylindrical, attached to corals. 



Distribution, imbedded in corals, chiefly in the tropical seas, round the world. 



* The name, Nobia, is given in this work on the authority of Loach, but this 

 must be a mistake, probably caused by some MS. name, (that fertile source of 

 error in nomenclature), having been used. 



