I36 PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



Corallum an attached lamina, without hydnophoroid protuberances— continued. 



Incrusting, nearly flat, calices nearly 0.5 inch (12.5 mm.) distant; interstices flat; columella? 



Astraa diffluens Q. and G. (non Lamarck) ■ - P- lahstclla Dana 



Corallum incrusting at base, from which rise numerous cylindrical lobes; longitudinal sharp 

 carina;, I to 3 mm. tall; calices 1.5 to 2 mm. in diameter; septa 24, primaries and sec- 

 ondaries equal; columella a single pointed papilla, often absent or obscure. .P. percarinata Ridley. 



Pavona cactus (Forskal). 



Plate 56, figures 1, la, views of a frond from the original material of Pavonia formosa Dana. 



1879. Pavonia cactus Klunzinger, Korall. Roth. Meer., pt. 3, p. 73, plate 9, fig. 2. 



1906. Pavonia cactus von Marenzeller, Denksch. k. k. Akad. Wiss. Wien, vol. 80, p. 90, plate 23, fig. 77- 



Klunzinger and von Marenzeller have discussed the synonymy of this species, 

 the type species of the genus, and I have made notes on it on pages 132 and 133 of 

 the present paper. It is my belief that Pavonia formosa Dana and Lophoseris 

 knorri Milne Edwards and Haime should be added to its synonymy. 



Distribution.— Red Sea, thence eastward to Tahiti. 



Pavona venusta Dana. 

 1846. Pavonia venusta Dana, U. S. Exploring Expcd., Zooph., p. 326. 



Recently I have been able to examine the type of this species in the Museum of 

 the Boston Society of Natural History, and a few fragments have been presented to 

 theU. S. National Museum. Dana's original description is excellent. The most 

 nearly related species is P. ■pratorta Dana. In P. venusta there is a more con- 

 spicuous tendency for the septo-costae to alternate in size and around the calicular 

 margins the principal septa are more prominent than the intermediate septa. 

 The elevation of the margins of the principal septa causes the calices to be slightly 

 tumid around the edges. In the arrangement of its septo-costae and principal 

 septa it resembles P. danai, but the latter has much larger calices and coarser 

 septo-costae. From the information at present available to me, P. venusta appears 

 to be a valid species. 



Locality.— Dana gives no locality for the type, but it evidently came from 

 the Indo-Pacific region. 



Pavona danai (Milne Edwards and Haime). 

 Plate 55, figure 2, specimen from Cocos- Keeling Islands; plate 56, figures 2, 2a, type of the species. 

 1846. Pavonia boletijormis Dana, U S. Expl. Exped., Zooph., p 327, plate 22, fig. 7 {non Lamarck). 

 i860. Lophoseris danai Milne Edwards, Hist, nat Corall., vol. 3, p. 71. 

 1867. Pavonia complanata Verrill, Proc. Essex Inst., vol. 5, p. 44. 

 1879. Pavonia annularis Klunzinger, Korall. Roth. Meer., pt. 3, p. 72, plate 9, fig. 7- 

 1879. Pavonia laxa Klunzinger, Korall. Roth. Meer., pt. 3, p. 73. 

 1907. Pavonia decussata Bedot, Madreporaires d'Amboine, p. 229, plate 35, tigs. 180-182. 



The following is a description of a specimen from Cocos-Keeling Islands: 

 Corallum frondose, fronds dissected, edges acute, thickened gradually toward the base, 

 8 mm. thick 4.1 mm. from the edge, forms compact, almost solid, lamina; curved or with 

 flattish sides, not pronouncedly crispate; no carinae on fragment here described. 



Calices bifacial, arranged in definite, short, or indefinite rows roughly paralleling the 

 growing edge. Distance between rows from 2.5 to 5 mm., usually about 3 mm.; distance 

 between calicinal centers in the same row from 1.5 to 4 or 5 mm. Calicular cavities 1 to 1.5 

 mm. in diameter parallel to septo-costae; from size stated up to about 3 mm. along line ot 

 rows Depth about I mm. The intercalicular ambulacra are fiat, crossed by alternately 

 larger and smaller septo-costae. About 5 (2 large and 3 small) septo-costae to I mm., the 

 larger ones about 0.5 mm. apart; sides of the larger densely beset with perpendicularly 

 projecting, blunt-ended, fine granulations, between which the septal lamellae show as white 



Septa in the subcircular calices 12 to 18 in number, alternately larger and smaller, the 

 larger extending to the columella; in the elongate calices the number may reach 28 or 

 30 Within the calice the small septa are thin and do not reach the columella, while the 



