90 SPONGES. 



SPONGIA MAMMILLARIS (Halichondria mammillaris). Plate XXIII. 



I cannot identify it with any in Dr Johnston's works ; but it may 

 be analogous to the mammillaris. 



This substance completely invested u valve of a shell, by a thick coat- 

 ing, completely applied to the outer surface and covering over the inner : 

 so that, were it removed, it would form a perfect Scotish bonnet. 



The external dimensions of the sponge are four inches by three and 

 a half: the surface is convex, following the shape of the shell. From the 

 surface about seventy of what resemble yellowish leather tags, somewhat 

 flattened, and from eleven to thirteen lines high, and a line and a halt' 

 across at the base. These tags rise out of the substance of the sponge. 



A few ran within, from the portion turning over below, and some 

 ran without. 



The latter are farther prolonged within these three days ; and more 

 slender a great deal than the tags above. 



This is the Spongia mammillaris of Muller's Zoologica Dauica, torn. iv. 

 p. 44, plate 158. His specimen is infinitely inferior to mine ; but, he 

 remarks, that his description was taken from it as preserved in spirits. 

 He gives a general view of the surface, and a transvere section shewing 

 the texture ; and comprises the description in two or three lines. 



The mammillae of my specimen resemble exactly the teats of n cow. 



PLATE XXIII. 



Spongia mammillaris. 



