. Polycystins, figures of remarkable forms &c. in the Barbados chalk deposit (chiefly collected by Dr. Davy, and noticed in a lecture delivered to the Agricultural Society of Barbados, in July, 1846) . , and by himsent tx) IMr. Rails. Professor W. C. Williamson saw it whenin Mrs. Burys hands (October, I860,) and kindly suggested itmight possibly lie a Surirella. 3 & 4.—Varieties of Dictyospiris (?) Ehrenberg. 5. Actiniscus (?) of Ehrenberg and Pritchard; a triangular net, like a Diotyocha, but wth a solid centre, which centre (or nucleus)gives the idea of being capable of stretching up into a
. Polycystins, figures of remarkable forms &c. in the Barbados chalk deposit (chiefly collected by Dr. Davy, and noticed in a lecture delivered to the Agricultural Society of Barbados, in July, 1846) . , and by himsent tx) IMr. Rails. Professor W. C. Williamson saw it whenin Mrs. Burys hands (October, I860,) and kindly suggested itmight possibly lie a Surirella. 3 & 4.—Varieties of Dictyospiris (?) Ehrenberg. 5. Actiniscus (?) of Ehrenberg and Pritchard; a triangular net, like a Diotyocha, but wth a solid centre, which centre (or nucleus)gives the idea of being capable of stretching up into a Podo-cyrtis-like form ; sides of triangle measure .0065 ; there are nineouter and six inner cells, arranged rouud a solid-lobed andpmictured nucleus, which bears one long and two short spines. 6.—A Desmidia-like, but silicious, clear, transparent plate, with wa^•ededges, and a perforated centre. Appears to resemble in somedegree, Lithodesmium undulatum, of Ehronbergs Kroide-biidung, page 76. Dr. Wallich suggested (from sketch) thatit might be a part only of some polycystinous form. 7. ^Tlie uppei part like Ehrenbergs Podocyrtis cothurnata, but with a tubulous prolongation of the th^u^^l-^^- ■, USA PLATE Vni. IIG. 1, 2, 3, & 4.—Varieties of Haliomma. Ilaliomma Ilumboldtii (?) ofEhrenberg, from Cambridge, Barbados, numerous and there are sometimes indications of spines radiatingfrom the centre, as in Stylodictya, yet the points romid tlie ed<^eapjiear to be merely marginal aiipendages.—Diameters, in-cluding spines, from .0077 to .0085. 5, & 0,—Miiller describes these as stages of growth oi the Haliomma,where the outer web is spiiming itself over and the centralnucleus, and the siliceous rafters or supports extending like aframework from the micleus to the exterior covering. (Page 21of Thalassicollen Polycystineu, «&c., des Mittelmeeres.) 7 & 8.—Spines or Spicules in Barbados deposit.
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