88 BRITISH PALALOZOIC FOSSILS. [Zooruyta, 
DirPHYPHYLLUM GRACILE (M’Coy). Page 88, figs. d, e, 7. 
Ref.—M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. 
Sp. Ch.—Corallum forming large masses of cylindrical tubes two lines in diameter, dichotomously branch- 
ing, and occasionally coalescing laterally ; surface 
marked with sharp longitudinal lamellar strize, about 
four in one line; vertical section, shews transverse, 
very slightly convex, thick, smooth, regular diaphragms 
reaching nearly across the tube, two interdiaphragmal 
spaces in one line, bent downwards at the cireum- 
ference ; lateral vesicular area extremely narrow (less 
than one-fourth the diameter, of about one layer 
of cells ; horizontal section, primary radiating lamellze 
thick, equal, extending less than half-way to the 
centre, leaving the broad, smooth diaphragms, or clear 
space in the middle nearly two-thirds the diameter ; 
between each pair of primary, in some specimens, is 
an extremely minute marginal lamella. 
The small diameter of the tubes distinguishes 
this species easily from any other Diphyphyllum 1 
know, and gives the whole much the appearance of Clisiophyllum turbinatum.—a. Old specimen, natural size, shewing the 
1° c imbricating interruptions of growth, and costal edges of lamell# in the 
Siphonodendron aggregatum (M Coy), but the lamellee worn upper portion; 6. horizontal section, natural size, shewing the large, 
* ie Q =P partially radiated vesicular tissue of the inner or axal area, the equal lamelle 
do not extend nearly to the centre ; there is no axIs, in the middle area and the very narrow, unequally developed outer or peri- 
3 = : thecal zone ; ¢. vertical section and form of terminal cup, natural size of small 
and the dichotomous fission of the star and tubes specimen, shewing the proportions and direction of the cells of the three 
may be distinctly observed. arees jandethe solid defining lines apart, as well as the section of the mesial 
te Vs : Diphyphyllum gracile. —d. Small portion of mass, shewing the natural 
Position and. Locality —N ot uncommon 1 the size of the tubes; e. HOPED Becnon of a tube magnified slightly, shew- 
. \ : o G ‘4 a ing the very small radiating lamella, and the thick, straight divisional 
impure limestone of Lowick, Nor thumberland. median line indicating a true dichotomous fission ; f. sections in the hori- 
zontal and vertical directions shewing the broad transverse diaphragms, 
with pucks narrow, complicated, deflected edges, bearing the short radiating 
lamelle, 
MMe, 
> 
S 
Yi 
PYNOMe 
GaN Sh 
BASS 
GtagsSsSs 
GENS 
AN 
a HSS 
DIPpHYPHYLLUM LATESEPTATUM (J/°Coy). Pl. 3. C. fig. 10. 
fief —M°Coy, Ann. Nat. Hist. 2nd Series, Vol. III. p. 8. 
Sp. Ch.—Stem upwards of eight inches long, cylindrical, about three lines in diameter; nearly smooth, 
faintly striated longitudinally, and obsoletely wrinkled concentrically ; vertical section, middle area occupied 
by slightly irregular transverse diaphragms, extending across two-thirds the diameter of the tubes, about 
four in the vertical space of one line, their edges abruptly bent downwards; lateral area very narrow, of 
nearly equal width, the inner composed of one set of small horizontal plates, the outer of two rows of 
minute, curved, vesicular plates inclining upwards and outwards. 
This species differs from the D. concinnwm (Lonsd.) of the carboniferous limestone Kast of the Ural 
chain, in the great proportional width of the transverse medial plates, which average two-thirds the diameter 
of the stem, or three times the width of the two outer areas of one side in the present species, but 
average one-third the diameter of the stem, or about equal to the two outer areas of one side in the other. 
The dichotomous mode of division of the stems (characteristic of this group among the septate corals), and 
also the conical upward projections of the centre of the transverse lamellae immediately under the point of 
fissure, were very well shewn in many of the specimens. 
Position and Locality Abundant in the carboniferous limestone near Corwen. 
Explanation of Figures —P\. 3. C. fig. 10. Small portion of mass, natural size.— Fig. 10a. Do. 
Vertical section magnified three diameters, shewing the three areas, apparently dichotomous mode of division 
of the parent stem, and conical elevation of the transverse diaphragms below the point of fissure; the top 
