646 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxii. 



as in A. mauritiana. The pedicels continue to the veiy edge of the 

 collar, on which the papilhe are larger than over rest of dorsum. 

 Superficiality the retracted papilhe resemble pedicels, but since there 

 appears to be no perforated terminal plate such as is well developed 

 in the pedicels, they are not to be ranked with the latter. The sup- 

 porting rods and plates are, however, well developed toward the top 

 of the papillae. (See below.) 



The cak^areous ring has no posterior prolongations, but anteriorly is 

 deeply scalloped. The exact shape is best shown b}" the figure. (Plate 

 LXVII, fig. 2(7.) There are two large Polian vesicles and one short, 

 twisted, madreporic canal embedded in the dorsal mesentery. The 

 madreporic body is prominent and lies on the left side of the mesen- 

 tery. The gonad is still small, and forms a tuft on the left side of the 

 mesentery, behind the madreporic canal. Left branch of respiratory 

 tree much longer than right. Cuvierian organs relativel}' large. 



Both tables and buttons are very numerous in the perisome, the 

 edges of the former overlapping, or at least loucliing. The buttons 

 which lie beneath the tables also imbricate irregularly. The disk 

 of the tables is 0.08 to 0.09 mm. in diameter and is ])ierced by eight 

 peripheral holes and a central larger one. Frequently there are sev- 

 eral small accessory perforations. Rim is smooth, slightl}' undulating: 

 the spire is robust, and is made up of four upright pieces slightly flar- 

 ing at the crown, which is armed with inunerous teeth, whose arrange- 

 ment is best shown by the tigures. Buttons are large, smooth, and 

 vary considerably in size, but average 0.1 mm. in length. They are 

 broadly elliptical and the six or eight holes are rather small in propor- 

 tion to the whole button. Man}" of the buttons are rather wider in 

 proportion to length than the figures here given. Some buttons have 

 five holes, and a few four or nine. Occasionally a button is incomplete, 

 a portion of the outer rim being wanting. Supporting rods and plates, 

 two types of which are figured (Plate LXVII, fig. 2/), are abundant 

 in the wails of the pedicels and papilla^, where also tallies are present. 

 The rods and plates grade into large buttons in the proximal portion 

 of the pedicels and papillfe. In the pedicels the plates are more abun- 

 dant than the supporting rods and are slightly larger than those in the 

 papilla?, averaging 0.15 to 0.20 nun. longest dimension, although 

 smaller ones are present. There are also very large buttons in the 

 pedicels with twelve or thirteen holes. The terminal perforated plate 

 of the pedicels is well developed and measures 0.5 mm. in diameter, 

 the perforations about 0.015 mm. 



This species is a shore form, inhabiting tide pools in lava rock 

 and on coral reefs. Since the gonad is still very small the specimens 

 are probably immature, as their size would suggest. This wide rang- 

 ing form, which Bedford" believes includes flavocastanea, is found in 



«Proc. Zool. Soc.; 1898. 



