72 F. A. SMITT, 



denticle, thus between this and the named rostrum producing, in a manner, a secon- 

 dary sinus, reminding of the corresponding feature in the Retepora cellulosa and Ret. 

 rosacea; still, at other times, this denticle totally wants, and the latero-distal part of 

 the margin of the aperture raises itself uniformly. As a rather curious variety we 

 may cite the colonies, in which the oral avicularium, of a very constant form, with an 

 elongate, rounded rectangular aperture, of the form as shown in the fig. 236 (highest 

 in the figure), of about the same breadth as the zooecial aperture, raises itself on some 

 of the zooecia only, while the other zooecia want the avicularium, in being provided 

 only with an acute rostrum (mucro). This, in the Discopora albirostris, not uncom- 

 monly seems to be the case. In the Discopora pusilla, in the above-named cylindrical 

 stem, the same deficiency of the rostral avicularium is to be observed. That specimen, 

 furthermore, presents the ocecia, which elsewhere have been wanting in the Floridan 

 Discoporcv examined. These ocecia are elevated, in the middle above their aperture 

 sometimes pointed, with a rather wide mouth. Between them and the zooecial rostrum, 

 one pair of denticles usually is developed, which perhaps answers to marginal bristles, 

 thickly calcified, although on other zooecia, deprived of ocecia, between these denticles, 

 three bristles of the ordinary, slender form are placed on the distal part of the aper- 

 tural margin, thus supporting the supposition, the denticles rather will answer to the 

 above-named secondary raising of the lateral margin of the aperture. 



Discopora pertusa (Pl. IX, fig. 182, Pl. XII, figs. 240 and 241). 



Char.: Zooecia ovata, ventricosa, erecta, tota fronte poris pertusa (vel interdum 

 strato secundario calcificationis imperforato, nitido obducta) aperturam prsebent semi- 

 ellipticam (cujus latitudo circ. =0,31 mm.), margine proximali concavam, ad articulatio- 

 nein operculi interdum coarctatam, parte latero-distali secundaria libere erectam; avi- 

 cidario ad aperturam proximali muniuntur obliquo, mandibulo obtuso clauso, quod in 

 apertura secundaria immergitur. 



Hah'.: In proff. 35 — (30 orgyarum hujus speciei colonias tuberiformes Coraliis in- 

 sidentes haud frequentes cepit Pourtales. 



The most appliable character for this species, particularly in its worn condition, 

 as its size and outer appearance will confound it with the Cellepora gigas, is the pre- 

 sence, in the secondary zooecial aperture, of a more or less rounded oral avicularium, 

 in an oblique position, together with the uniform, secondary raising of the latero-distal 

 part of the aperture. Its true affinity, on the other hand, evidently is proved by the 

 form of its primary zooecial aperture, which places it at the side of the last preceding 

 species. From this, however, it differs by the constriction at the articulation for the 

 operculum, although that character, sometimes, scarcely is perceptible. In that case, the 

 low position of the oral avicularium will distinguish it, together with- the uniformly 

 porous zooecial wall, although this last character, sometimes, is concealed, by its cove- 

 ring itself, secondarily, bj 7 a shining, continuous layer of chalk. From such a colony 

 the fig. 182 was taken. Still, in taking away that layer, the pores become apparent. 



