48 MADREPOEARIA. 



29. Porites Antigua 3. (P. Antiguce tertia.) (PI. II. fig. 6 ; PI. X. fig. 7.) 

 [Antigua, coll. Gregory ; British Museum.] 



Description. — The corallum develops tangles of tall, stout, branching stems, of nearly 

 uniform thickness, 1'5 to 2 cm. thick, forking at wide angles which, however, gradually 

 change into rounded curves, as the prongs bend up into the vertical. The terminals are thick 

 and mostly swollen and flat-topped at the tips. The branches of adjacent stems fuse together. 

 The crowding of the stems seems to be the cause of the forking being at irregular distances ; 

 single prongs may grow straight up for 5 cm. with only slight indications of knee-bends 

 (= abortive attempts to fork, see p. 18) before beginning really to fork. The living layer 

 seems to be about 7 cm. deep. 



The calicles are large, slightly under 2 mm., nearly superficial. The walls are low and 

 thick, consisting of an irregularly zigzag arrangement of the meeting of the septa of adjacent 

 calicles without any differentiation of a distinct wall-tliread ; the thickness of the thread varies 

 according as the septa are thin or thick and flaky (on under surfaces and near the basal 

 parts of the living layer). The septa throughout are mere rough projections from the walls, 

 of various lengths and showing no conspicuous radial symmetry. The pali are large, rough 

 granules, not very prominently raised and very irregularly joining with the septa. The inter- 

 septal loculi are not conspicuous, being irregular, straggling breaks into the interior with here 

 and there one large one. The columellar tangle is fairly compact and for the most part carries 

 a large central tubercle. All the granules are roughened, and, as the skeleton thickens, tend 

 to spread into flakes. 



The section shows the periphery for about 2 mm. as a fairly close network of radial 

 trabeculse and stout concentric rings. Within this cortical layer it becomes nearly solid. 



The colour of the dried corallum is a dark sepia. 



This coral differs in growth-form and in size and character of the calicles from any of 

 the other known branching forms from Antigua. There is an approach to whorl-formation of 

 the branches where the. forking has been disturbed by overcrowding, such as is also seen in a 

 part of the large type specimen of Lamarck's Porites fur cata in Paris (see below, p. 82). But 

 the calicles of the two corals are not alike according to the descriptions. 



a. Zool. Dept. 99. 6. 26. 2. 



h. A stem which seems to have fallen over. Zool. Dept. 99. 6. 26. 3. 



30. Porites Antigua 4. {P. Antiguce quarta.) (PI. II. fig. 7 ; PI. XVII. fig. 4) 



[Antigua, coll. Gregory ; British Museum.] 



Description. — The corallum is explanate and massive with thick, free, expanding edges 

 showing only slight drooping. Successive growths appear to pile up on one another with 



