510 Mr. R. Kirkpatrick on 



nuclei, one of which is situated centrally and the other peri- 

 pherally, is common. A later stage in which the peripheral 

 spermatocyte has formed by division a mass, 18 /jl in diameter, 

 of spermatids is also common (PI. XIII. fig. 11). One ripe 

 cell has burst, liberating a cloud of spermatozoa. The head of 

 a spermatozoon is oval, 2*7 /x long, at one focus homogeneous 

 and refringent, but at another focus showing a very dark 

 portion, whence the tail originates, and a clear terminal area 

 (PI. XIII. fig. Ha). 



Chemical Composition. — Dr. G. T. Prior of the Mineral 

 Department applied Meigen's test by boiling some powdered 

 skeleton in solution of nitrate of cobalt, and obtained the 

 reaction for calcite. Accordingly the composition is similar 

 to that of Petrostroma schuhei Doderlein. 



Subfamily Merlinje, no v. 



Pharetronidse in which the solid skeletal framework is con- 

 structed of vertical main beams of fibrillar cement, from each 

 of which there radiate three vertical flanges to meet similar 

 flanges from other columns so as to form cylindrical tubes; 

 the latter are partitioned off by horizontal floors, a honeycomb- 

 like structure resulting. Solid framework without axial core 

 of spicules. 



In the subfamily Lithoninas the framework is constructed 

 on the bSton arme principle ; in Merlinse the be'lon is not 

 anne, the axial stiffening of spicules being dispensed with. 



Merlia, gen. nov. 



Merlinte encrusting ; with the dermal membrane supported 

 by tufts of slender tyles, and with rhaphides ; tuning-fork 

 spicules present. 



Merlia normani, sp. n. 



The specimens consist of four small dried pieces of rock 

 material, each encrusted by a thin layer of the sponge. The 

 ruck-fragments formed part of an agglomerated mass of 

 broken shells, worm-tubes, corallines, &c, about the size of 

 a man's fist, obtained from 60 fms. off Porto Santo Island 

 near Madeira, by Senhor Adolpho 0. de Noronha, and given 

 by him to Canon Norman, who entrusted the specimen to 

 me to describe. 



Two of the smaller pieces have been used up for vertical 

 and horizontal sections. 



The largest specimen forms a very thin crust 14 x 7 mm. 

 in area, and with thin edges. The surface is covered with a 

 cream-coloured membrane and has an extremely fine uni- 



