with descriptions of new Species. 335 



terminal twigs regularly bifurcating, the branches have conse- 

 quently a dichotomous arrangement : papillae placed rather far 

 apart, small, of equal size, and arranged in a single row along the 

 branches, the direction of which they distinctly indicate on the 

 surface of the matrix. Spicula of two kinds ; the larger about 

 ^yth of an inch in length, generally a little bent, stout and in- 

 clining to fusiform, with the pointed end gradually tapering ; the 

 opposite extremity provided with a rounded head, somewhat ellip- 

 tical, and merging imperceptibly into the shaft. The smaller 

 spicula are about ^rd the length of the larger ones, and are less 

 stout ; they bend gradually in the centre, from whence they taper 

 to a fine point at each end. 



I have seen only one specimen of this species; it is in Pecten 

 maximus, most probably from Orkney, and extends from the beak 

 to the ventral margin. The spicula somewhat resemble those of 

 C corallinoides, but are considerably stouter; and though the 

 heads are large and well-formed, they are not so distinctly marked 

 as in that species; and the smaller ones bend less abruptly : the 

 character of the branches is also remarkably different. 



The walls of the excavations of this species are rather finely 

 punctured. 



C. muscoides. PI. XV. fig. 11. 



Sponge formed of numerous delicate, much- divided, closely 

 and irregularly anastomosing branches, with the terminal ones 

 very slender and composed of an open network ; the principal 

 branches about -j-^^th of an inch thick, and distinctly seen rami- 

 fying throughout the general interlacement of the sponge : pa- 

 pillae small, very numerous, approximating, and where the ana- 

 stomosis is extensive, without apparent order ; towards the ter- 

 minal branches however they run in rows, and betray the course 

 of the branches on the surface of the shell in which the specimen 

 is buried. Spicula of two kinds, one with heads, the other with 

 both ends pointed ; the former, measuring y| gth of an inch in 

 length, are generally straight, proportionately stout, and with 

 two globular heads, one terminal, though not always perfectly so, 

 and one placed at a little distance down the shaft; occasionally 

 there is an additional head a little way below the second ; from 

 this end the shaft tapers gradually to a sharp point at the oppo- 

 site extremity, towards whicli there is frequently a slight bend. 

 The other kind of spicula are fusiform and as stout as those with 

 heads, but only half their length ; they taper gently to both ends, 

 wliich are finely pointed, and bend abruptly in the centre, where 

 there is frequently a nodulous swelling ; there is also occasionally 

 another indistinct nodule or two on each side of the centre one 

 and at some little distance from it. 



