10 FOLKE FOLKESON, MADREPORARIA. 



Three small specimens from the contents of the stomach of a Tetrodon; nos. i and 

 k are very worn. 



Costae of two kinds: the primaries, secondaries, and tertiaries are almost equally 

 developed and extend down to the base; they are somevvhat broader than the costae 

 corresponding to the septa of the fourth cycle and have more irregular granulations than 

 the latter ones, which have only one series of very regular granulae and are not quite so 

 prominent as the other costae; the costae of the fourth cycle do not reach the base. Calice 

 is open and seems rather shallow, partly owing to the worn state of the upper parts of 

 the septa. Septa in four cycles; they are arranged in the manner peculiar to the 

 genus Heterocyathus. Paliform teeth are especially prominent in no. h, in which the 

 small, papillose, depressed columella is somewhat more markedly delimited than in 

 the other specimens. 



I have referred these specimens to H. aequicostatus E. & H., though the bad con- 

 dition and the insufficiency of the materials do not admit of an exact determination. 

 I am inclined to think, however, that they are only varieties of //. aequicostatus E. & 

 H., perhaps only small specimens of this form. 



Heterocyathus alternatus Verrill 1864 (Figs. 10—11). 



Heterocyathus altemata Verrill 1864 (30), IV, p. 149; 18G6 (30), V, p. 41, plate 2, figs. 6, C a. 



Though there is no specimen of this species in Dr. Mjöberg's collection, I here 

 mention it in connection with the discussion of the species of Heterocyathus. 



In the collection of the Swedish State Museum there are 8 specimens from un- 

 known locality, and 1 specimen from West Australia, which in every respect agree with 

 Verrill's description. As, however, neither the description nor the figure clearly show 

 that the septal fusions, characteristic of the other species of Heterocyathus, are typ- 

 ical of this species also, and the original figure is not quite distinct, I have published two 

 photographs. The septa of the fourth cycle soon join by their bending septal edges 

 with the septa of the third cycle, and in the centre of calice they perfectly fuse; in the 

 centre the septa of the third and fourth cycles, thus fused, also run together with those 

 of the second cycle. 



As in the other species of this genus, the septa of the fourth cycle, which run on 

 either side of those of the first, show a tendency to become more developed than 

 those which run on either side of the septa of the second cycle. Still the septa of the 

 fourth cycle in height and breadth are inferior to those of the third cycle. In that 

 respect, H. alternatus shows a marked difference from H. aequicostatus E. & H. More- 

 over the calice of H. alternatus V. is very shallow: even in the larger specimens the 

 distance between the columella and the level of the highest (primary) septa does not 

 exceed I — 1,5 mm. 



All specimens are purely white. 



The measurements, in millimetres, are as follows: 



Height . . . 



4,2 



4 



3.4 



3,4 



3,2' 



3 



2,7 



2,7 



2,2 



Diameter . - 



10 



9 



9 



7,8 



8,7 



7 



7 



ti, G 



5,5 



figured. 





















