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Zoopuyra.] UPPER PALAZOZOIC RADIATA. 
Subfamily. NEMATOPHYLLINE. Sce page 33. 
Genus. NEMATOPHYLLUM (M°Coy). 
Ref —M°Coy, Ann. Nat. Hist. 2nd Series, Vol. III. p. 15. 
Gen. Char.—Corallum composed of numerous, inseparably united, polygonal, prismatic tubes, each having a 
straight, thin, flat, fillet-like solid, or nearly solid, axis, from which, in the horizontal section, the fine numerous 
radiating lamellze are seen extending directly to the walls; radiating lamellze connected by very fine trans- 
verse dissepiments, only visible externally in the outer area: vertical section shews three distinct areas: first, 
the thin flat axis; second, a sharply defined cylinder of small vesicular arched plates, the rows directed 
from the axis obliquely downwards and outwards; outside this is the third area of similar small arched plates, 
forming a minutely vesicular structure, slightly smaller than that of the inner zone, but the rows directed 
obliquely upwards and outwards ; reproduction by small circular buds, developed within the area of the parent 
star. 
In mode of reproduction and tri-areal structure this genus approaches Strombodes (as above understood), 
from which it differs altogether in the nature of the axis, which in all the species of that genus is cylindrical, 
composed of numerous plates variously twisted together, and giving a cellulose section in every direction, but, 
on the contrary, forms a thin, flat, simply solid lamina in the present group, and is exhibited in a vertical 
fracture, either as a narrow opaque white line, or as a broad ribbon-like fillet, according to whether the section 
is in the direction of its width or across it. A further difference is constantly observable between these groups in 
the vertical section, which is, that the interstitial vesicular plates of the inner area in Strombodes have their rows 
either nearly horizontal, or inclining obliquely upwards from the axis towards the outer wall, while in Nema- 
tophyllum, on the contrary, they converge towards the axis aboye and incline downwards and outwards below, 
so as usually to meet at a considerable angle those of the outer area which incline in the usual direction 
upwards and outwards towards the walls. This peculiarity in the inclination of the interstitial vesicular plates 
of the inner area produces a marked difference in the stars on the weathered surface in the two genera, causing 
the inner area to form a large prominent oval or conical boss in Nematophyllum, and a flat or deeply-hollowed 
cup in Strombodes. A third difference between these generic groups is, that in the latter, the vertical radiating 
lamellz are principally confined to the inner area, not existing in most of the species at all in the outer area, 
and do not reach the walls; while, on the contrary, all the radiating lamelle in Nematophyllum arise from the 
outer walls, are strongest in the outer area, and only half of them in general penetrate the inner area. In the 
latter corals also, the whole vesicular structure is much more minute and delicate in stems of the same size 
than in the others, and the cells of the inner area are larger than those of the outer, which is the reverse of what 
we find in Strombodes. As the young columns are produced from circular buds continuing their development 
within the walls of the parent, it results that the stems are inseparably united; the walls defining the stars 
being one simple plate, the joint production of the adjacent polypes, cannot be divided, and consequently, 
vertical fractures of the mass, instead of exposing the flat striated external surface of the stems, pass invariably 
through the substance of the coral itself, exposing only sections of the interior; the eternal walls being 
only seen in those rare cases shewing the extreme limits of a mass, or where in a section two masses may have 
coalesced. Some of the species resemble C/isiophyllum, but are distinguished by the peculiar axis, and by 
the cells of the inner area being larger and fewer than those of the outer. The genus is, I believe, exclusively 
Paleozoic. 
NEMATOPHYLLUM ARACHNOIDEUM (M"Coy). PI. 3. A. fig. 6. 
ftef—M Coy, Ann. Nat. Hist. 2nd Series, Vol. III. p. 16. 
Sp. Ch.—Stars with from four to seven angles, and averaging from six to nine lines in diameter; ais 
very thin, one line wide; vertical section, inner vesicular area wider than the outer, of little-arched plates 
inclining slightly downwards from the axis; it takes about two (rarely one) of those plates to reach from 
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