with descriptions of new Species. 333 



bent, not particularly stout, and sometimes slightly inclined to 

 fusiform, but tapering pretty gradually to a sharp point at one 

 end ; the other furnished with a well-defined globular head ap- 

 proaching to ovate with generally a terminal point. 



This appears to be the most destructive species to oyster-shells, 

 and abounds in the Frith of Forth. It is undoubtedly the C. 

 celata of Grant : the form and large size of the spicula are suffi- 

 cient to distinguish it. The C. celata of Dr. Johnston, however, is 

 most likely another species, as the spicula are somewhat different. 



C. insidiosa. PI. XV. fig. 5. 



Sponge when dry of a brown colour, branched ; the branches 

 about y\ths of an inch thick, irregular, anastomosing : papillae 

 distant, irregularly arranged, rather small. Spicula yyyth of 

 an inch long, stout, sometimes slightly fusiform, but generally 

 tapering gradually to a fine sharp point at one end, towards 

 which it is generally slightly bent ; the other extremity is fur- 

 nished with a large globular head separated from the shaft by a 

 distinct dusky line, and mostly a little flattened like the head of 

 a pin. 



This species, which occurs in Tridacna gigas, appears related to 

 C. gorgonioides ; like it this has only one kind of spicula, and in 

 both they are furnished with a rounded head. A cross section 

 of the excavations of this form has much the appearance of a 

 similar view of those of that species. I have not been able to 

 trace the terminations of the cavities, and therefore cannot speak 

 to their form. The short, stout spicula of C. insidiosa with their 

 large pin-like head are very characteristic, and readily distinguish 

 it from its congeners. 



C. gorgonioides, PI. XIV. figs. 1 & 6. 



Sponge of a bro\vnish yellow colour, branched, anastomosing; 

 the principal branches stout, sometimes nearly ^th of an inch 

 thick, irregularly rounded, or depressed, placed somewhat par- 

 allel to each other, and much zigzaged, giving off lateral 

 branches at the angles, which branches unite with those ad- 

 joining : terminal twigs thin, tapering to a fine point and bifur- 

 cating : papillse large, frequently almost y gth of an inch in dia- 

 meter, penetrating the surface of the shell or other matrix with- 

 out appai'cnt order, and placed considei-ably apart from each 

 other. Spicula very numerous, large and stout, measuring g'^^th 

 of an inch in length ; at one end there is an oval swelling which 

 is frequently some little distance from the extremity : from thence 

 the shaft gradually tapers to the other end, which is sharply 

 pointed and is generally much bent, pai'ticulax'ly towards the 



