366 MR. A. DENDY ON WEST-INDIAN CHALININB SPONGES. 



The smaller of the two large specimens (PI. LXI.) differs slightly in external appear- 

 ance from the one just described. The tubes are broader in proportion to their length, 

 and more inflated, narrowing towards the mouth. The spinous processes on the surface 

 also show a strong tendency to become confluent, and frequently form longer or shorter 

 ridges, running in various directions, with deep grooves between. This tendency to 

 form ridges is visible also to a certain extent in the larger specimen, but is not nearly 

 so well marked. 



Locality. Nassau, Bahamas. 



The third specimen in the collection, already referred to as belonging to a slight 

 variety, consists of a single wide tube, 24 centim. in height and about 8 centim. in 

 diameter across the mouth. It is now of a dirty greyish-yellow colour. It differs from 

 the types in two respects : — (1) the processes on the outer surface are not nearly so 

 strongly developed, being represented by low warts and ridges ; (2) there still exist within 

 the fibre a very few vestigial oxeote spicules, apparently in the last stages of absorption. 

 The specimens agree so closely in other respects that it is impossible to separate them 

 specifically; so that we have here, as in the case of Sjpinosella plicifera, an excellent 

 illustration of the gradual replacement of spicules by spongin. 



Locality. Jamaica. 



Spinosella velata, n. sp. (Plate LIX. fig. 2.) 



The single specimen in the collection (PL LIX. fig. 2) consists of five irregularly 

 cylindrical or somewhat compressed tubes of various sizes, united together at their 

 bases, and two of them also united laterally at points where they come into contact 

 with one another. The height of the sponge is 19 centim., and the greatest breadth 

 13 centim. The largest tube measures about 45 centim. in diameter at the top. The 

 actual aperture of the tube, however, is very much reduced in size by the presence of 

 a broad, horizontal, circular diaphragm, which projects inwards from the wall of the 

 tube at a distance of some two or three millimetres below the free margin. This 

 diaphragm is the most characteristic feature of the species and that from which the 

 specific name has been derived. It exists in all the tubes, but is more developed in 

 some than in others, and is broadest in the largest tube, measuring 1-5 centim. in 

 greatest width. The free margin of the three larger tubes is only slightly irregular in 

 outline and not spinose, while that of the two smaller tubes is distinctly spinose. The 

 diaphragms also are for the most part smooth, but bear spinous processes on the upper 

 surface in the case of the two smaller tubes. The outer surface of all the tubes is 

 distinctly spinose. 



The true oscula are small and circular and occur abundantly scattered over the inner 

 surface of the tubes. The walls of the tubes are marked with a distinct series of 

 longitudinal veins. 



The main skeleton consists for the most part of an irregular reticulation of fairly 



