606 APPENDIX A. (LONSDALE ON CORALS.) 
Lithostrotion mammillare. 
Columns irregularly aggregated; axis cylindrical, formed of twisted, conical, separable plates; inner 
zone narrow ; outer zone broad, arched plates highly inclined, wholly traversed on the upper surface 
by vertically discontinuous lamellte; inner surface of walls strongly ribbed ; terminal star, boss pro- 
minent, spirally twisted; surrounding , depressed area deep, lined by the lamellae of the inner zone ; upper 
band or outer zone broad, more or less inclined, crossed by numerous lamellte ; boundary between the 
stars projecting, sharp, crenulated. 
Fig. a. Terminal perfect surface, natural size. 
Fig. b. Vertical section exhibiting the peculiar characters of the axis, natural size. 
Astrea mammillaris, Fischer de Waldheim, Oryc. Gouvern. de Moscou, p. 154. pi. 31. figs. 2, 3. (Lime- 
stone of Tessovo ; siliceous nodules near Moscow.) 
This species is distinguished from the other three, described in these memoranda, by the peculiar cha- 
racters of the cone-in-cone plates of the axis ; from Lithost. emarciatum, it differs in addition to that 
marked structure in the vaulted plates of the outer zone being almost wholly traversed by lamelliferous 
laminae ; and from Lithost. astroides, by the great amount, in that species, of complicated reticulations 
and blendings of the three areas, whereby great care is required in detecting the existence of each. 
The only specimen examined was a siliceous cast, three and a half inches wide, three broad, and one 
and a half thick ; and it apparently formed pait of a circular mass, the columns radiating rapidly from 
the thickest side. The upper surface consisted wholly of terminal stars, well-preserved, but irregularly 
grouped, and it indicated considerable inequalities of growth (fig. a). The siliceous mode of preservation 
did not permit the structural details to he fully ascertained. 
(1.) The axis (fig. b) sometimes presented in fractured surfaces, a persistent cylindrical body, similar 
to that of Lithost. emarciatum, but there was constantly at the lower extremity a conical indentation as 
well as a total absence of all traces of a reticulated structure. These hollows were exhibited on the 
under surface of every transversely fractured column, and presented casts of conically-twisted plate* 
which appeared to be easily separated, and altogether unconnected vertically by intermediate laminae. 
(2.) The narrow, inner zone was not so preserved, that its characters could be well ascertained ; and 
there were indications of a much greater intermingling of its component parts with those of the outer 
area, than in Lithost. emarciatum. That it formed in the original condition of the coral a distinct struc- 
tural division, was nevertheless evident from smooth semicylindrical casts on the inner side of the external 
zone (fig. b), and from the occurrence, in one case, of a perfect cylindrical cavity surrounding the axis 
The lamellae were apparently thin, and of uniform breadth ; and the interstices presented casts of curved 
transverse or connecting plates. 
