TRIBE I. ASTR^EACEA. 253 



disks become elongated, and sometimes sinuous, with two or three 

 polyp mouths, show a transition to the Meandrinse. This is exempli- 

 fied in the A. dipsacea, A. uva, A. deformis, and A. favosa. The 

 length of the trenches is often limited in the different species, inas- 

 much as the number of polyp-buds, which may thus form, without 

 an external subdivision, has generally its limits. 



The union of the polyps, which are contained in the same cell, or 

 under the same disk, appears to be of the most intimate kind ; there 

 is a free internal communication from one polyp to another of the 

 same series, in place of the imperfect cellular connexion, which sepa- 

 rates two Astrsea polyps ( 77). 



The Meandrinae attain the same gigantic dimensions as the Astraese, 

 and with equal symmetry of form. The sinuous lines of polyps, pre- 

 senting the same varied tints as in the preceding groups, give great 

 beauty to the zoophyte when alive and expanded ; the domes seem to 

 be covered with a network of flowering vines. 



These corals are confined to the warm coral-reef seas, and grow 

 within twenty fathoms of the surface. 



This genus was separated from the old Madrepora by Lamarck, to 

 include the corals with meandering cells. Ehrenberg instituted the 

 genus Manicina for the species which grow from a central attach- 

 ment (explanato-glomerate), from which we have separated the Cteno- 

 phyllise and the massive meandering Mussse. The species retained 

 as Meandrinse are simply meandering Astrase. Independently of the 

 mode of growth, the Mussa are readily distinguished from them by 

 their larger size, the coarse dentation of the lamellse, and having one 

 or more lamellse ranging along the bottom of the trench ; the Mani- 

 cince, by their larger size and neat denticulation ; and the Ctenophyllice, 

 by their very stout, remote, and nearly entire, lamellae. 



The genus Astrsea affiliates with the Meandrinae along several lines. 

 The A. dipsacea is thus related to M. cerebriformis ; A. favosa and 

 reticularis, to M. labyrinthica and M. phrygia ; A. deformis to M. 

 dedalea; and the A. favulus to M. filograna. 



The species dedalea and spongiosa might be transferred without 

 impropriety to the genus Astrsea, as the trenches are very short, and 

 many contain but a single cell. 



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