WEST INDIAN ISLANDS PORITES. 57 



40. Porites St. Thomas 2. {!'. Sancti-Tlwmw semmda.) (PI. XT. fig. 1.) 

 [St. Thomas, coll. M. Ducliassaing ; Paris Museum.] 



Description.— T\\e corallum rises into branching cylindrical stems, forming tufts. The 

 forkings are at rather wide angles, with thick round terminals (1 ■ 3 cm. across). The living 

 layer extends 7 cm. 



The calicles are large, 2 mm., superficial except at the tips, where the walls are slightly 

 raised. The walls are thin, sharp, zigzag threads, but in older parts the skeleton thickens 

 rapidly and the thin thread appears as if resting on a broad zigzag flake (see Appendix, p. 143). 

 The septa are conspicuous, sometimes continuous, sometimes as radial rows of 2 to 3 granules 

 from which the pali are hardly distinguishable. Seen from above the septa are laterally very 

 echinulate, the echinula; obscuring the long interseptal loculi, wliich are further affected by the 

 development of an echinulate columellar tangle which appears to fill the calicles. The pali (6) 

 are chiefly distinguishable in the younger deeper calicles. In the older calicles they are 

 somewhat confused with the granules upon the septa. 



The section is an open flaky reticulum. 



This description is based upon notes made in the Paris Museum, where the specimen 

 is preserved as Z 182&. The remarkable echinulation of the skeleton leads me to think that this 

 must have been one of Duchassaing's type specimens of his P. davaria, because he placed it 

 under a heading " Septis palhUisque hirtis." If so, we gather from tlie description that the 

 living coral was of a rust colour, sometimes of a more or less deep wine red. The tentacles 

 are of the same colour, but get paler and paler towards their tips, which are hardly coloured 



at all. 



Though the branching is not unlike that of Lamarck's P. davaria, there is no 

 echmulation of the skeleton in that coral, hence, according to Duchassaing's own system, based 

 upon the presence or absence of echinulse, the two are specifically distinct. 



41. Porites St. Thomas 3. (P- Sandi-Tlwmw tertia.) (PI. III. fig. 4; PI. XL fig. 4.) 



[St. Thomas, coll. Duchassaing ; Paris and Turin Museums.] 



Syn. ? Fmitcs Solanderi Duchassaing and Michelotti, Mem. sur les Cor. des Antille.s (1860) p. 83; 

 and Suppl. (1864) p. 95. 



Description.— The corallum forms compact clusters of short, thick, almost pear-shaped 

 lobes with large flat tops, so that the whole stock is squat and low. 



The calicles, apparently about 1-5 mm., are flush with the surface. The walls are 

 delicately lamellate, often incomplete, and show traces of the tendency to break up into con- 

 spicuous denticulations. They are beset with delicate echinulations. The septa are also 

 echinulate, as are also the pali, which are visibly the inner ends of the septa, and are 5 to 6 



I 



