BULLETIN 50, UXITKl) STATES XATION.U^ MUSEUM. 213 



which surrounds the cokuiu'lhi, tnH-onic nuich thickened, so thiit deep down in tiie 

 coralhte tiie cokimella is rather solid. .Minute o;ianuhitions on the .septal faces. 



Locality. — "Loo Choo Lslands."' The locality name for the specimen on which the 

 above description is based, is not followed by an interroiration point. 



13. PORITES DISCOIDEA Studer. 

 I'hilc I.X.WIX, li^'. -1. 

 1901. I'orites (UscoideaiiTVUKK, /oul. .hiluh., Syst.. .XL, p. 4L'."i, |>l. xxxi, lig. ll). 

 Description. — Studers description is as follows: 



The coralluin is a free plate, 3 mm. thick and 92 nun. in diameter; the upiKT surface i.s tiat, show- 

 ing only a single elevation, which was caused by .Scr/di/d tubes. One-half of the siJt'cimen is grown 

 upon a second plate that is ilead and in places projects beyond the edge of tlie overlying layer; the 

 living portion is therefore spread over a dead lower layer. 



The lower side shows a thick, linn, concentrically wavy epitheca. which gives to the whole plate 

 a rock-hard, brittle constitution, while tlie layer bearing the calices is oidy 1-1. .5 mm. tliick. The 

 mai^in is acute and forms an irregularly rounded contour. On one place it is somewhat elevated. 



The calices on the upper surface are small, distinctly limited, pali and columella recognizable with 

 the naked eye. The diameter of the calices is as much as 1 mm. The wall consists of loose, fused 

 trabecuhe, which terminate above in fine, branched spinules. The septa are only slightly prominent; 

 on their margins and faces are spiny ridges of loose texture, standing directly in relation with the 

 system of mural trabecule, and from them the spiny pali surrounding the columella rise interiorly. 

 As the calices are very shallow, the pali reach almost to the level of the mouths of the calices. 



This species is separated from /'. lidu », which jiossesses a similar habitus and was obtained in the 

 Sandwich Islands by the Clialleiigir, by its smaller and shallower <alices and the strongly developed 

 pali. These in P. lichen, according to Quelch, are only slightly prominent. 



Laysan. 



Remarks. — Later, in de.scribinj;- /'. liclnn. it will be iwinted out that Quelch 

 was wrong when he identitied his specimens from the ■Sandwich Islands" with 

 that species (see pp. 214,215). The verj- characters which Professor Studer says 

 dirt'erentiate his P. discoiden from P. lichen are the same as in that species. How- 

 ever, /'. discoidea is different from lichen. Professor Studer's figure shows none of 

 the depres.sed rows of calices conunon in /'. lichen, and a different septal formula is 

 indicated. P. discoidea probably belongs in the /'. lobata group. 



Professor .Studer has kindh- sent me a photograph of his ty])e of this species. 

 The species is peculiar in the comparatively poor development of the concen- 

 tric skeletal elements. The interseptal loculi appear decidedly open; even the 

 ring of palar .synairtuula is usually only partially de\eloped. The se])tal arrange- 

 ment is a dorsal directive, four lateral pairs, and the ventral triplet with the inner 

 ends of the laterals of the triplet directed toward or fusing to the inner end of the 

 ventral directive. The normal iunnl)er of pali is six. They are present on the 

 inner ends of the dorsal and ventral directives and before the lateral pairs. The 

 columella is a compressed tubercle, lamellar in character, and connects the ends of the 

 two directives across the axis. 



This species is very dilb-rent troni l>ana's /'. lichm. and is only snperliciallv 

 similar to C^uelch"> erroneously identitied /'. liiluii from the Sandwich Islands," 

 which is a vountr corallum of /'. lobata. 



"Bernard, Porites of the Indo-Pacific Region, p. WS, pi. ix, Hg. 9; jil. xii, fig. 5. 



