94 PORIFERA. III. 



39. H. pugio n. sp. 



PL IX, Fig. 7. 



Incrusting ; surface somewhat hispid. Spicula: megasclera; the skeletal spicules acanthostyli with 

 a distinct head, only spined on the lower part, they are divided into tivo groups, large 0-38 0-54""", 

 small 0*12 o-2o mm ; the dermal spicules thin styli 0-27 o-ji mm ; microsclera two forms, chela arcuala 

 0-021 0-040"'"', sigmata, small and curved in a somewhat circular way, plane or nearly plane, 0-014 



Of this species we have one specimen, growing on a stone; it forms a thin incrustation of a 

 greatest extent of about 2o mm , and the thickness does not exceed 0-5 mm . The colour (in spirit) is white. 

 The surface is somewhat hispid from the projecting acanthostyli. The dermal membrane is thin and not 

 separable, sparingly provided with dermal spicules, but somewhat more richly with chelae. A number 

 of circular openings of canals are seen shining through the membrane. 



The skeleton. The dermal skeleton is not much developed ; it consists of dermal spicules which 

 are, so far as I could ascertain, lying partly more or less horizontal in the membrane, but for the 

 greatest part projecting. The main skeleton consists of acanthostyli with the heads placed on the 

 substratum; it is rather dense with the spicules close-standing; the longest of the styli project through 

 the dermal membrane. The heads of the styli are at the base inserted in a somewhat slight mass 

 of spongin. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli which are straight or only 

 very slightly curved and taper evenly into a long apex; the head is round and not large but distinct. 

 They are spined at the base and some way out, but the larger apical part is smooth; the spines are 

 small. With regard to size the styli are divided into two groups, but otherwise they are quite similar. 

 The large styli have a length of 0-38 0-54 mra with a diameter at the head of 0-021 o-O28 mm ; the small 

 styli are 0-12 o-2O rara long and the head 0-015 0-021 mm thick. The small styli are the most numerous. 

 2. The dermal spicules are rather thin styli which are cylindrical, straight or slightly curved and 

 taper into a long and fine point The length is 0-27 0-31"' with a diameter of about 0-003 mra . 

 b. Microsclera are of two forms, chelae arcuatae and sigmata. i. The chelae have a sometimes rather 

 strongly curved shaft and relatively small end-parts; the alae are lobe-shaped but somewhar*narrow, 

 the tooth is elliptical. The size of the chelae is somewhat variable, the length being 0-021 0-040""" 

 and the thickness of the shaft 0-004 0-006 mm . 2 - The sigmata are very small and fine and they are 

 somewhat circularly curved, so that the length is not much greater than the breadth; they are plane 

 or almost plane; the length is 0-014 0-017 mm and the thickness o-ooi mm or still finer. Both forms of 

 microsclera are seen especially in or near the dermal membrane. 



Embryos. The specimen contained a great number of embryos; they are globular or lentiform 

 and they were easily seen in the thin sponge on account of their white colour. They have an average 

 diameter of 0-35 mm . They contained either no spicules or also developmental forms of the chelae but 

 no megascleres. 



Locality: Station 15, the Denmark Strait, 66 18' L,at N., 25 59' Long. W., depth 330 fathoms 

 (bottom temperature -=- o 75 C.). Only one specimen. 



