ASTR.EOPOR^ rULVINAT.-E. 91 



Group II.— ASTRiEOPORJl PULVINATJ!. 



Those forms in which the calicles rise up like a slieaf of corn above the epitheca, the top expanding and 

 hanging over. Under the pendent edges of (lie. expanded Idster-like top, a secondary epitheca maij 

 appear. This expanded tup is grown over hy fresh layers, until great, smooth, cushion-shaped masses 

 are formed. 

 Species C. Astrsopora listen. (Pis. XXVIIL, XXIX.; PI. XXXIII. fig. 12.) 



Z)fscr!:7)/{o«. — Corallum showing tlie typical pnlvinate type of growth. The large 

 cushion-shaped masses of the adult often developed from the dead fragments of previous 

 growths which have been overturned. Secondary epitheca often well developed under tlie 

 new layer forming at any time the expanded top. 



Calicles crowded, young ones appearing in almost every available space; generally 

 circular, averaging 2 mm. ; slightly protuberant, with thick eclunulate walls, often developed 

 only on one side. When fully developed, globose or even almost cup-shaped, the echinulre 

 being bound together by trabecule. Three cycles of septa, of which the primary and some- 

 times also the secondary may be well developed. The former, on nearing the centre, curl and 

 break up into filaments which may interlace. The connection between the costal echinuhc and 

 the septa is very marked in the marginal walls of the calicles, when protuberant. In regions 

 of rapid growth, the calicles may all be immersed in a light reticulum, their walls being thin 

 and membranous. The youngest are minute membranous pits with no signs of septa. In 

 sections, the great growth in thickness and consequent lengthening of the polyp-cavities leads 

 to the frequent formation of tabula which may form continuous horizontal lines 2 to 3 mm. 

 apart through the whole corallum, dividing it into tiers. 



The canenchjTna shows great variations, according as the calicles are specially crowded 

 and rapidly growing, or not. When crowded, the interstices run like a network of deeply 

 engraved lines, which, however, may be almost filled up with a light reticulation showing no 

 traces of the typical ccenenchymatous te.xture of the genus. As a rule, the costal elements 

 are more prominent than the synaptieular, which appear reduced to simple trabeculte. No 

 continuous floors are distinguishable in the interstices. The more typical echinuln? run out 

 at their tip into minute spines. Ccenenchyma as a rule delicate, may, in large specimens, be 

 very coarse. 



I was at first inclined to look upon the specimens on which the above description is 

 based as identical with Lamarck's Astraa jiuMnMria. As already stated, I was ultimately 

 compelled to accept Lamarck's statement that A. pulvinaria wa.s perhaps only another torm 

 of A. myriophthalma. His description of A. imhinaria shows that it belonged to the explanate 

 forms which are very distinct from the large bolster or cushion-shaped growths of the type 

 now under discussion. 



"While, therefore, I have adopted Lamarck's name pulvinate to denote a special form of 



N 2 



