ME. A. DENDY ON WEST-INDIAN CHALININE SPONGES. 301 



The main skeleton (PL LVIII. fig. 7) is a well-developed, more or less polygonally 

 or subrectangularly meshed reticulation of stout horny fibre. The fibre is stouter and 

 the reticulation closer in the veins than elsewhere. The average diameter of the fibre 

 is about 0-04 millim., but there is a good deal of variation in this respect ; it is sparsely 

 cored by slender oxeote spicules, which are much more abundant in the primary than 

 in the secondary lines, being commonly arranged in the former in a somewhat plumose 

 manner, while in the secondary lines they are for the most part scattered singly. 



The dermal skeleton is a polygonally close-meshed reticulation of slender fibre, 

 averaging in diameter about 0*012 millim. ; cored occasionally by single spicules. On 

 the inside of the tubes there is no dermal reticulation distinguishable, as such, from the 

 main skeleton. 



The spicules are slender oxea, usually slightly curved, measuring about - 082 by 

 0-0025 millim. 



Locality. West Indies. 



Spinosella sororia, var. dilatata, nov. (Plate LVIII. fig. 6 ; Plate LXIII. fig. 2.) 



This variety may be disposed of very briefly ; it is represented in the collection by 

 one fine specimen (PL LXIII. fig. 2), which differs from the typical form of the 

 species in its more luxuriant and bushy habit and in the much greater width of the 

 larger tubes. 



The specimen in question is 35 centim. in greatest breadth and 21 centim. high. 

 The tubes vary greatly in size ; the larger ones are more or less compressed, and the 

 largest measures 11*5 centim. across the longer diameter of the mouth. The spines on 

 the outer surface of the tubes are very strongly developed and very sharply pointed ; 

 but the venation on the inner surface is not nearly so strongly marked as in the typical 

 forms. Otherwise there are no differences worthy of note. The dermal skeleton is 

 represented in Plate LVIII. fig. 6. 



Locality. Bahamas. 



Spinosella sororia, var. fruticosa, nov. (Plate LIX. fig. 3.) 



This variety, of which there are two specimens in the collection, again differs from 

 the typical forms in its bushy habit, and the spines on the surface are again very 

 strongly developed. The tubes, moreover, are cylindrical and somewhat narrow in 

 diameter ; their walls are thicker than in the typical form, and the venation on the 

 inner surface is strongly marked. 



The specimen (PL LIX. fig. 3) which I consider as most typical of the variety 

 measures 30 centim. in greatest breadth, and 27 centim. in height ; the diameter of the 

 mouth of the largest tube is 3 centim., but this is somewhat exceptional. 



Both specimens are remarkable for the presence of a fine calcareous deposit or 

 crust on the outer surface of the tubes, which gives them a peculiar greyish-white 

 appearance. When treated with hydrochloric acid it effervesces strongly, and on mi- 



