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Show 332 DR. J. S. B O W E R B A N K ON T H E SPONG1AD.E. [Mar. 18, Fig. 4. An end view of one of the dentato-cylindro-hexradiate spicula, magnified 530 linear. 5. A malformed specimen of the dentato-cylindro-hexradiate form of spiculum, magnified 530 linear. Malformations of this spiculum are not uncommon. 6. An average-sized acuate skeleton-spiculum, magnified 80 linear. 7. One of the spicula from the interstitial membranes, magnified 80 linear. PLATE XXX. Ecionemia acervus, Bowerbank. Fig. 1 represents a fully developed fusiformi-acerate skeleton-spiculum, magnified 80 linear. These spicula vary to a very considerable extent in size. 2. A full-sized attenuato-expando-ternate connecting-spiculuin, magnified 80 linear, 3. A fully developed attenuato-recurvo-ternate connecting-spiculum, mag- 80 linear. 4. Two of the subtuberculated fusiformi-cylindrical tension-spicula from the dermal membrane, magnified 530 linear. 5. One of the subsphero-attenuato-stellate retentive spicula, magnified 530 linear. 6. A minute cylindro-sphero-stellate retentive spiculum from the interstitial membranes, magnified 530 linear. By an accidental omission, one of the minute and slender acerate tension and external defensive spicula was not figured as intended. Those spicula are identical in form with the one represented by fig. 10 in the present Plate, from Ecionemia densa, the only difference being that those of E. acervus are much less in both length and diameter. Ecionemia densa, Bowerbank. Fig. 7 represents one of the fusiformi-cylindrical skeleton-spicula, magnified 80 linear. 8. One of the attenuato-expando-ternate connecting-spicida, magnified 80 linear. 9. A portion of a larger specimen of an attenuato-expando-ternate connecting- spiculum, the radii of which are cylindrical, magnified 80 linear. 10. One of the small and slender acerate tension-spicula, from the interstitial membranes, magnified 80 linear. 11. Two of the tuberculated subcylindrical tension-spicula from the interstitial membranes, magnified 530 linear. 12. An attenuato-stellate entirely spined retentive spiculum, magnified 530 linear. 13. One of the cylindro-sphero-stellate entirely spined retentive spicula, magnified 530 linear. 14. A cylindro-sphero-stellate retentive spiculum, radii spineless, magnified 530 linear. Dictyocylindrus setosus, Bowerbank. Fig. 15 represents a portion of a terminal group of seta**, from the distal end of the sponge, with a small piece of the dermal membrane and its characteristic spicula, magnified 80 linear. 16. One of the flexuous cylindrical skeleton-spicula from the axis of the sponge, magnified 150 linear. 17. An acerate spiculum from one of the seta?, magnified 150 linear. PLATE XXXI. Pachymatisma inconspicua, Bowerbank. Fig. 1. One of the subfusiformi-acerate skeleton-spicula, magnified 80 linear. 2. An average-sized superexpando-ternate attenuated connecting-spiculuin, magnified 80 linear. These spicula vary greatly in their size and |