HIC KSON— POLYTREMA 



453 



Sporadotrema, but I believe that the resemblance between the two species is not so 

 close as he anticipated from the examination of his worn specimen. 



The description of the species may be amended as follows : 



Test composed of more or less erect sinuous laminae arising from a spreading 

 encrusting base. The free margin is thick and crenated. 



Colour, salmon -red. 



The surface of the vertical sides is perforated by foramina and exhibits a pattern 

 of lenticular convexities corresponding with the subjacent series of chambers (Plate 31, 

 fig. 12). In the larger specimens the convexities are obscured in the lower or basal 

 parts of the surface. The internal structure of the laminae consists of two parallel 

 series of chambers whose outer walls are pierced by foramina. The chambers communi- 

 cate with each other by wide cylindrical passages. Between the two series of chambers 

 interlocular spaces occur at the free edges but these spaces become closed up with 

 growth of the chamber walls, so that, at and near the base of the lamina there are 

 no interlocular spaces (Plate 32, fig. 25). 



At the edge of the laminae the upper portions of the chambers are free and exhibit 

 a cock's comb row of short tubes as in S. eylindrieum. 



The larger laminae in my collection are from 15 — 20 mm. in length, from 7 — 8 mm. 

 in height and from 1'5 — 2 mm. in thickness. 



The species differs very noticeably from S. eylindrieum in shape. The large and 

 perfect specimens in my collection show that it does not break up into branches com- 

 parable with the branches of S. eylindrieum. In some of the larger specimens several 

 laminae arise from a common spreading base and are united together to form a plexus 

 or labyrinth. I have not, at present, been able to determine whether this is due to 

 concrescence or irregular ramification. Carter's expression that the laminae are "united 

 mesenterically " is not very clear to me, but it may be intended to signify that the 

 edges of some laminae are united with the vertical sides of others in the formation of 

 the labyrinth. 



Carter correctly describes the colour of his specimen as pinkish red. It was, as 

 already stated, very much water-worn and probably dead when dredged up. The colour 

 may have been as dark in tone as my specimens when it was alive. In the older parts 

 of the laminae where the outlines of the chambers can no longer be recognised in the 

 surface view, the foramina are 07 mm. in length and 0"03 mm. in diameter and are 

 distinctly tabulate (Plate 32, fig. 25). The chambers vary a good deal in size but are 

 approximately 07 mm in horizontal length and 0'5 mm. in depth. 



IV. DISTRIBUTION. 



Polytrema miniaeeum (Pallas). 

 Syn. Millepora miniaeea Pallas 1776. 

 Polytrema eorallina Risso 1826. 



The only specimens of this species that I have found in Professor Stanley Gardiner's 

 collection are from Providence (D. 8) 125 fathoms and Coetivy. 



SECOND SERIES— ZOOLOGY, VOL. XIV. 58 



