ASTR^OPOR^ EXPLANAT.E. 89 



lu view of the great amount of variation shown by these specimens of A. myriophthcthna 

 there is liardly any necessity to consider Lamarck's Astrcm puivinaria as a variety of viyri- 

 ophthalma as he himself suggested. We may safely assume the two to be specifically identical, 

 Lamarck's description applies better to an encrusting explanate growth somewhat massive and 

 cusliion-like (j)ulvinata), but with uneven surface {iindosa) such as is shown Ijy specimens of 

 inyriophthalma, than to a form exhibiting wliat I have called tlie pulviiiate * type of growth. 

 Further, Dana described a species which he identified as It&maxck' a puivinaria ; this, however, 

 has been renamed " profunda " by Verrill. And, lastly, MUne- Ed wards' description of the 

 species "pmlvinaria " appears to be compounded of Lamarck's and Dana's descriptions, which, 

 as we have just seen, referred to different types. 



Species 4. Astrffiopora incrustans. (PI. XXVII. ; PI. XXXIII. fig. 10.) 



Description. — A thin encrusting growth, creeping over and hanging nearly perpendicularly 

 down around the substratum. When the epitheca is well developed, the pendant edge turns 

 up ; where it is not able to grow as fast as the coenenchymatous skeleton, the latter hangs 

 down irregularly, imbedding everything that comes in its way. 



Calicles round, projecting only on slight prominences or humps ; on smooth surfaces, 

 immersed ; when projecting, the wall is very irregular, one side often thick, the other thin, or 

 even not developed, so that the calicles face in all directions. The calicles vary greatly in 

 size, from 2 • 5 to 1 mm. diameter. Two cycles of septa visible at the margin, with indications 

 of a thii'd ; the first cycle becomes very pronounced deeper do%vn, almost meeting at the centre. 

 There is great variation in the appearances of the calicles ; the last two cycles may be very 

 marked round the margin, dividing it into lobes, or, again, the septa may be barely visible at 

 the margin, only appearing far down, in which case the aperture is nearly round, with slight 

 irregularities. These latter calicles are larger, and may be indicative of rapid growth. The 

 fossa appears slightly conical, especially in the abnormally large calicles which occur in the 

 highest parts of the corallum. The smaller, more flower-like, well-marked calicles are about 

 twice their diameter apart, the larger are more crowded. 



The canenchyma shows also great variations : between the smaller regular calicles, the 

 synapticular element is well represented, making the texture look solid, the costal element 

 being stout and irregular, giving a rough, granular look to the surface. In regions of more 

 rapid growth, the ccenenchyma is a light, friable reticulum, which tends to be flaky. The 

 vertical costal elements are predominant on the higher portions, the synapticular on the 

 sloping. 



There is, unfortunately, only one specimen of this coral. On one side of the mound, all 

 the calicles are small and almost star-like, and on the other, large and round, and it is 

 impossible to .say, without comparison with other specimens, which is the typical character of 

 the species. There is reason to think that the foraier may be the more normal type of calicle, 

 and that the latter is due to abnormally rapid growth. If that could be established by new 



• On the origin of this term from Lamarck's specific name, see p. 83. 



