15^ 



figured they occur in about four rows, with three or four peristomes in each row. At the 

 margin of the roof of the ovicell a few peristomes are outlined on their central side, where 

 they project into the region of the ovicell ; while peripherally they are continuous with the 

 honeycomb-like arrangement of prismatic spaces which is seen in the rays. Between these 

 partially isolated zooecia runs a sharply marked, but low calcareous ridge, by which the ovicell 

 is outlined. In the interval between two rays seen opposite the left half of the upper border 

 of the ovicell in fig. i , the honeycomb has been closed by the development of a porous 

 calcareous plate across the opening of each tube. In all other parts of this specimen the 

 ovicell is in contact, peripherally, with the system of open tubes which form the frontal surface 

 of the colony, including its rays. 



The ooeciostome cannot be distinguished with certainty, but I believe this to be due 

 to the fact that it has a close resemblance to one of the isolated peristomes of the central 

 region. The lowest member of the middle vertical row of zooecia, in fig. i, is probably the 

 ooeciostome. 



The ovicell of the younger specimen (348. I.) is similar to the one already described, 

 but the calcification of its roof is not quite complete. The whole of the rest of the frontal 

 surface of the colony is honeycomb-like ; and the rays are only just commencing to be indicated. 

 Measurements, in u. ; 



Greatest diameter of the colony, fig. 1, 5,500; 



Width of the two broadest lobes, 1,300, 1,100 ; 



Width of ovicell, 1,850; 



Diameter of orifices, 145. 



Supercytis digitata was described by D'Orbigny 1 ) from Cretaceous material. The recent 

 form to which Busk 2 ) gave the same specific name (as Fasciculipora digitafa), apparently by 

 an undesigned coincidence, has usually been regarded as identical with D'Orbigny's species, 

 although I am not sure that this view is correct. D'Orbigny's fig. 8 represents a colony with 

 two distinct ovicells. One of these (right of figure) has lost its roof; and, as D'Orbigny 

 pointed out, it shows "en dedans un canal qui communiqué avec 1'intérieur de la colonie". 

 This clearly indicates that the ovicell is to be regarded as a modified zooecium ; the aperture 

 shown by D'Orbigny being the point where the dilated part of the ovicell communicates with 

 its proximal undilated part. The other ovicell is said to be complete. If this was really the 

 case, it may be concluded that the ovicell in the Cretaceous form is developed in such a way 

 as not to include any zooecia. This fact, and perhaps the existence of two ovicells, may be 

 taken as a sufficiënt reason for distinguishing the recent species from its Cretaceous ally. 



The specimen (Brit. Mus. 75. 5. 29. 60) described by Busk in 1875 from Cape Capricorn, 

 Oueensland, seems to be distinct from the 'Siboga' specimens-, while the figure given by the 

 same author, in the 'Challenger' Report (1886) of "Supercytis digitata" 1 appears to show that 

 that specimen has an ovicell of a different type, and that it cannot be referred either to S. 



1) D'Orbigny, 1854, t. cit., p. 1060, PI. 798, figs 6 — 9. 



2) Busk, G., 1875, t. cit., p. 37, PI. XXXIII, lig. i. 



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