230 MADREPORARIA. 
241. Porites Dar-es-Salaam (yl. (P. Africana orientalis prima.) 
[Ras Rangoni, coll. Dr. Ortmann ; ? Museum. | 
Syn. Porites reticulum Ortmann, Zool. Jahrb. vi. (Syst.) (1892) p. 654. 
Deseription—The corallum, growing up among the “Sea-grass,” branches almost from 
the ground, to which it is very lightly attached. The branches are 8 em. long, very irregular 
in shape, knobbed and lobed, from 1 to 2 cm. thick, often fusing, especially near their tips, 
which then appear flattened. The ultimate branchlets are short, knobbed, and rounded, or else 
bluntly pointed. 
The calicles are quite superficial below and nowhere deepened, about 1 mm. in diameter. 
The walls on the tops of the stems rise as a network of thin lines above the level of all the 
rest of the surface. The septal edges are broken up into teeth, of which the pali form the 
innermost ring, but without being raised above the level of the rest and of the columellar 
tubercle. 
This coral obviously owes its growth-form to the grass, one influence of which is to hold 
the sand still and allow corals to settle. Coral growth is impossible where the waves keep the 
sand in motion. 
Other Porites recorded from the Dar-es-Salaam Reefs are— 
1. Several specimens, some hemispherical and attached to the rocks of the Chokir Bank, 
and other small free nodules found among the grass of Ras Rangoni. All these the author 
proposes to identify with Porites lutea of Milne-Edwards, which is one of the well-worn names 
freely attached to Porites from all parts of the world, whereas it belongs solely to the form from 
Tongatabu and its characters are described on p. 34. (Cf. also p. 244, where will be seen 
some account of the origin of the confusion.) 
2. Several lobed (? branched) masses found loose in the sea-grass, which Dr. Ortmann 
believed to be specifically identical with the P. Red Sea 3, called by Dr. Klunzinger 
“nodifera.” 
3. A specimen said to resemble the Red Sea form No. 1 (Porites solida of Forskal), which 
has been identified by Dr. Klunzinger, because it is the Porites which supplies much of the 
building stone on the shores of the Red Sea. Dr. Klunzinger has given a full description with 
photographs. Dr. Ortmann’s specimen was found on the rocks of Chokir Bank. 
4. Specimens which Dr. Ortmann claims to be older, and more developed colonies of the 
Red Sea coral (No. 7), described by Dr. Klunzinger as “ Porites echinulata.” In two of the 
forms a few cylindrical columns arise 1 cm. thick and 4 cm. high. These may repeatedly 
divide, and the calicles on them have sharper and thinner walls. They were found on the 
Upanga Reef. 
The difficulty of identifying Porites even when one has the forms in one’s hand is so 
great, that it would have been safer if these forms had all been properly described by the 
author and not simply referred to certain supposed species. 
