. The Annals and magazine of natural history; zoology, botany, and geology. oup themselves at points about one fourth the length of the sjiicule from one or both of its extremities. Measurements : Diameter of gemmules 0-036 inch, skeleton-spicules 0*0068 by 0-0002 inch ; length of average dermal spicule 0-00066 inch, of gemmula spicule 0-00145 inch. Habitat. Incrusting stones in shallow Lakes or ponds in the vicinity of Hearts Content, New-foundland, collected by Mr. A. H. MacKay. All the specimens of this sponge came from the neighbourhood ofHearts Content, but whether they we
. The Annals and magazine of natural history; zoology, botany, and geology. oup themselves at points about one fourth the length of the sjiicule from one or both of its extremities. Measurements : Diameter of gemmules 0-036 inch, skeleton-spicules 0*0068 by 0-0002 inch ; length of average dermal spicule 0-00066 inch, of gemmula spicule 0-00145 inch. Habitat. Incrusting stones in shallow Lakes or ponds in the vicinity of Hearts Content, New-foundland, collected by Mr. A. H. MacKay. All the specimens of this sponge came from the neighbourhood ofHearts Content, but whether they were gathered Irom a lake uponthe heights or from a brook mentioned by Mr. MacKay near thesea-level does not seem entirely clear. The accompanying illustra-tion (magnified 225 diameters) will suggest the peculiarities of itsskeleton, dermal and gemmular spiculation. The striking resem-blance of the dermal spicules to the minute birotulates, heretoforeonly known in a corresponding position in the case of MeyeniaEveretti, will at once impress the student. These are, however,. 246 MisceUaneous. more variable in size, are occasionally spined, and liave their raysmore prolonged and more delicately terminated. It is in the singular character of the spicules surrounding thegemmula3 that this sponge must attract peculiar attention. By thesystem of H. J. Carter, Esq., the freshwater sponges are now classi-fied into six genera, besides some conditional designations of formsin which the typical features are as yet undiscovered. These six,Sj>on(/illa, Meyenia, Beteromei/enia, Tahelh, Parmula, and Carteriiis,may again be associated into two groups, one of them including onlythe genus SpongiJla, characterized by the linear acerate spicules sur-rounding the gemmulae; and the other comprising all the othergenera, where the spicule of corresponding significance is a birotulate,or some easily recognized derivative of that type. Within this latterand larger group intermediate forms, connecting t
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