REPORT ON THE RADIOLARIA. 1693 



pores iu these circles is very variable, comiuoiily from three to nine, sometimes twelve 

 to fifteen or more ; their form is usually irregularly ovate (PI. 115, figs. 7, 9). The 

 bridges between the pores usually bear numerous siliceous threads or bristles, which are 

 curved downwards or upwards (PI. 115, figs. 4—6). Sometimes the spines are entirely 

 covered with similar bristles or cilia (PI. 117, figs. 2—5), more rarely with regular 

 verticils of lateral branches (PI. 117, fig. 6). 



The distal ends of the radial spines are simple iu Ilacckeliana (PL 114), whilst in 

 the other Circoporida they are usuall)^ (or perhaps constantly) either forked or armed 

 with a verticil of terminal branches. When the spines are simply forked, their two 

 terminal branches lie in certain meridional planes (PL 117, fig. 5). The same is 

 probably the case when they Ijear three divergent branches (PL 115, figs. 1, 2), 

 or four crossed branches (PL 117, figs. 4, 6). The larger species usuaUy bear a 

 corona of five curved branches disposed around the distal apex of each spine (PL 116, 

 fig. 3; PL 117, figs. 1, 2). Sometimes the formation of these coronas is twice or 

 more often repeated, so that the spines appear verticiUate. 



The centixd capsule of the Circoporida (PL 115, fig. 8; PL 117, fig. 6) is usually 

 about half as large as the enclosing shell, and lies excentrically in that half of its cavity 

 which is remote from the shell-mouth (PL 115, fig. 8). The other half (near the 

 mouth) is filled up by the cap-shaped, dark phaiodium. The proboscis, or the central 

 tubule of the astropyle, is hidden in the axis of the blackish phseodium, and is directed 

 towards the mouth of the shell ; it is often S-shaped, more or less curved. The circular 

 radiate operculum of the astropyle, placed on the base of the proboscis, exhibits 

 numerous branched radial ribs, and closes the main-opening like the lid of a tea-kettle 

 (PL 115, fig. 3). The number of the parapylse, or the accessory openings of the 

 capsule, which iu the majority of Ph.eodakia is two, seems to be usually increased in 

 the Circoporida. In Circoporus the capsule seems to possess six and in Circospathis nine 

 secondary openings, and therefore there is some probability that each circle of pores on 

 the base of a radial spine corresponds to a secondary opening of the capsule. In 

 Haeckeliana, however (PL 114), I could observe no parapylse at all. These accessory 

 openings are always very small in the Circoporida, and may be easily overlooked. 

 Futhermore, the number of observations respecting this difiicult point is too small, 

 and their certainty not satisfactory ; it rec^uires therefore further accurate examination, 

 as also does the whole central capsule of the Circoporida. 



The numerous and remarkable characters of shape and structure, which we have 

 described above as occurring in the Circoporida, are also found in the following closely 

 allied family, the Tuscarorida ; all the species are inhabitants of great depths. Perhaps 

 it may therefore be more convenient to separate these two families fi'om the other 

 Ph.eogromia as a peculiar order, under the name Ph.eocalpia. 



