4 C. F. JENKIN. 



NEW GENERA. The new genera, Hypodictyon* Dermatreton,\ and Tenthrenodes,^ 

 are introduced to contain the five new species which have " linked " flagellated 

 chambers. The term " linked " is here used to describe the peculiar arrangement 

 of the flagellated chambers in an open network or honeycomb pattern, so that a 

 large number surround each of the very large incurrent canals (intercanals). In 

 Sycon and Grantia the incurrent canals are usually smaller than the flagellated 

 chambers, and are each surrounded by only three or four flagellated chambers. 



Three of the new species have freely projecting distal cones ; two of these are 

 included in the new genus Tenthrenodes, in the family Sycettidse, and the third, 

 which contains chiactines, is in the corresponding genus Hypodictyon, in the family 

 Chiphoridse. The two remaining species have distinct dermal cortices, and are, 

 therefore, included in the new genus Dermatreton, in the family Grantiidse. The 

 dermal cortex is not continuous, but takes the form of a network covering the top 

 of the flagellated chambers, and is pierced by large holes corresponding to the spaces 

 (incurrent canals) between those chambers. 



The " linked " arrangement of the flagellated chambers appeared to resemble 

 closely the " grouped " arrangement described by von Lendenfeld (6) as occurring in 

 Sycantha temlla. As doubts existed concerning the accuracy of some of the details 

 of this description, it seemed advisable to re-examine the specimens. The author was 

 enabled to make this examination by the great courtesy of Professor von Lendenfeld, 

 who sent him all the remaining material he possessed. This material is 

 considerably macerated (as is stated by von Lendenfeld in his original description), 

 but is in quite good enough condition to allow the general structure to be ascertained 

 with certainty. The results of the author's examination show that all von Lendenfeld's 

 figures represent the structure correctly except Figs. 53, 54 and 56, which, though 

 no doubt accurately drawn, are quite misleading. The interpretation placed on the 

 figures by him appears, however, to be erroneous, and would seem to be due to the 

 unfortunate cross-section shown in Fig. 56. The true structure is best shown in 

 Fig. 57, representing a tangential section near the gastral cortex. This figure shows the 

 regular rectangular network formed by the chamber walls. The rectangles are alternately 

 flagellated chambers and canals, arranged like a chess board, exactly in the manner 

 shown in Haeckel's " Kalkschwamme," Fig. 13, Plate 60, as typical of his sub-genus 

 Sycocubus (sub-genus 3 of Sycandra). Haeckel's figure shows (correctly) the arrange- 

 ment of the flagellated chambers and inter-canals of Sycon schmidti ; this arrangement 

 only differs from that of Sycantha tenella in the shape of the flagellated chambers, 

 which in Sycon schmidti are approximately square (in tangential section), whereas 

 in Sycantha tenella, though still rectangular", they are much longer in one direction 

 (parallel to the axis of the sponge) than in the other (circumferentially). Sycantha 

 tenella is, therefore, a typical Sycon, remarkable for the size and regular arrangement 



* imo, under ; Starvon, a net. t bfppa, skin ; Tptjrus, holed. 



t,s, honeycombed. 



