42 BALANOIMIYLLIA. 



The y<)UiiL;-est individuals observed have the shape of a ti-imeated 

 cone attaehed Ity the luise. The wall is (juite smooth. iiiijiiTfoi-alf, and 

 the sej)ta, twelve in nuniher, etiual and not quite extending to tlie 

 centre, where the rudiments of tlie columella are already visible. At 

 this stage none of the family characters are displayed. The dimensions 

 are then about 2 mm. in diameter at the base, 1.3 at the calicle, and 

 .8 in height. The next step of development is the formation of costjc 

 on the upward prolongation of the wall. They first appear in the 

 shape of sharp jioints grouped al)out the origin of the septa. About 

 the same tiuu- an opening appears on the border and rather outside of 

 the calicle, opposite each of the secondary septa, which gradually 

 widens inwards, dividing apparently the septum in two. The two bor- 

 ders of that opening become the tertiary septa, the secondary septum 

 is gradually pushed inwards, and is replaced by a new one growing out 

 on the same radius from the wall, and Ijut loosely connected with the 

 joined tertiaries and original secondary. In a vertical section of an 

 adult specimen a row of perforations is seen to extend both on the old 

 and the new ])art of the secondary se])tum at the lines of junction with 

 the tertiaries. The interior ])art of the tertiary septum is now to all 

 intents and purposes a pal us, and the Avhole arrangement (juite similar 

 to that of Deltocyathus, for instance. At this stage the septa are 

 rather exsert and jagged on tlie l'{\'j:,v. and seen in profile the resem- 

 blance with Stephanophyllia is (piite striking, not taking the attached 

 condition into consideration. 



As the growth proceeds, the point of junction of tertiaries aud sec- 

 ondaries moves farther into the calicle, imtil it reaches the columella. 

 At this period the older or internal ])art of the secondary septum has 

 nearly or entirely disappeared, and the sauie process of growth goes 

 on with the septa of the fourth cycle, which become joined to those of 

 the third. 



One or two specimens sliow a coalescence of two individuals grow- 

 ing in a crowded position. 



Although this species is generally destitute of epitlieca. I hesitate in 

 separating from it a form of which a number of specimens were ob- 

 tained in G8 fathoms off tlie Tortiigas. These were ahiiost cylin(hica]. 

 covered nearly to the calicle by a thin wrinkled e])itheca. through which 

 the co.sta^ can be distinguished; the calicle contracted. All except a 

 few young ones were dead, and have all the appearance of having Ijeen 

 killed by being gradually covered with mud, as the calicle has mosth' 

 grown smaller aiul become stunted until defniitively smothered. Hav- 

 ing seen none of this form of a healthy growth, T am incliiu'd to 

 believe that they belong to Balitudp/ii/lliit Jhridiaiu, modified by external 

 circumstances. 



