ASTRiEOPORA. 83 



the straws in a wheatsheaf, expanding fan-like at the top. Under the drooping edges of the 

 bolster or cushion-like top a secondary development of epitheca is always found. Owing 

 to the death of the lower portions, the base at an early stage ceases to expand laterally, so 

 •that the ever expanding top causes the mass sooner or later to become top-heavy and 

 roll over (Plates XXVIII. and XXIX.). 



I have borrowed the name pulvinate from Lamarck's species pulmnaria, which I at first 

 thought might come into this division. It is true that Lamarck spoke of A. pulvinaria as 

 being only a variety of A. mi/rio2}hthalma. This suggestion, rejected by Ijlain\-ille, was 

 accepted — though reversed — by Dana, and again rejected by Milne-Edwards. It appeared 

 to me at first, that, as Lamarck mixed the Astrceoporce with a great number of specimens 

 of totally different genera in his single genus Asircca, two Astrteoporans would naturally 

 appear in such a heterogeneous collection to be very near to one another, and that the 

 suggestion need not be accepted. After a very careful examination of Lamarck's words, 

 I have, however, come to the conclusion that his description of pulmnaria (" incrustans, 

 undosa ") must apply to specimens showing the explanate type of growtli and not the 

 pulv'inate. Further, the prominent conical calicles ally it, as Lamarck suggested, with 

 inyriophthalma. Hence, after having accepted the species j)ulvinaria and made it the type 

 of the pulvinate method of growth, I found myself ultimately compelled to remove it again, 

 borrowing, however, the name " pulvinate " for the division. 



3. Globular Type. — The corallum commences at once to form a hemispherical mass by 

 the lengthening of the calicles, chiefly in the centre, while at the sides the coenench}Tnatous 

 skeleton rolls over the epitheca. At a later stage the corallum forms an almost perfectly 

 globular mass, composed of concentric shells, each being a new layer of growth, starting from 

 some point on the summit and creeping down all round. This division would contain 

 Lamarck's Astrav2)ora punctifera, which he describes as being like a small cannon-ball. 

 Lamarck added that his specimen showed no point of attachment. Tliis remarkable state- 

 ment (tliough quoted by Dana) has been generally allowed to drop, apparently as being 

 unintelligible. It appears, however, from the specimen in the Natural History Museum wliich 

 I identify with Lamarck's species, that these globes are, like the pulvinate specimens, liable 

 to break off and roll over ; it is, therefore, not difficult to see how the scar of attachment 

 might be grown over in a particular case (Plate XXX.). 



VARIATIONS PRESENTED BY THE CALICLES. 



These show considerable range of variation, in their average sizes, their distribution 

 (crowded or scattered), and in the way in which, when protuberant, they raise up the 

 ca3nench}"ma couically (cyUndrically or hemispherically). The structure of the wall 

 surrounding the aperture of the protuberant calicle is also of importance, as it is closely 

 associated with the character of the cojnenchyma, which is a marked feature in the genus. 



The niunber and character of the septa show also slight dillerences. 



M 2 



