346 Mr. A. Hancock on the Excavating Powers of Sponges, 



stomosing; the meshes frequently more than ^th of an inch 

 wide; lobes elliptical, about jth of an inch broad_, and giving 

 oiF numerous, minute, linear twigs : terminal branches dividing 

 dichotomously and furnished on all sides with twigs similar to 

 those of the lobes : the dichotomous arrangement may be traced 

 throughout the branches. Siliceous bodies of the surface very 

 numerous, measuring yfjth of an inch long and g-^^^th of an 

 inch broad, composed of two whorls, each comprising six or 

 seven squarish nodules ; the whorls being placed a little apart 

 from each other near the ends of a stout central axis which ter- 

 minates at each extremity in a nodule like those of the whorls. 



This is one of the largest and most beautiful of the excavating 

 sponges j only one individual has occurred : it is buried in the 

 substance of a large valve of Meleagrina margaritifera which has 

 been in my collection many years. The branches extend from 

 side to side of the shell, and reach from the beak almost to the 

 ventral margin, measuring in length six or seven inches. The 

 outer surface of this valve has unfortunately been removed, and 

 the papillary punctures consequently destroyed : the ramifications 

 of the lobed branches, however, are completely exposed, so that 

 they can be traced throughout. But a considerable number of 

 the terminal twigs remain imbedded in the shell, and are distinctly 

 seen through the inner transparent layer. 



The puncturing of the walls of the cavities of this species is so 

 strong that it may be seen even with the naked eye ; and they 

 are likewise penetrated with numerous small orifices for the 

 passage of the minute twigs which come from the underside of 

 the lobes. Whether similar twigs pass from the upper surface 

 I have not been able to determine, on account of the destruction 

 of the external portion of the shell. Those from the lower sur- 

 face puncture the innermost layer of the valve ; and as pearly 

 matter has accumulated around each orifice, the inside of the 

 shell is ornamented with numerous clusters, corresponding to 

 the lobes, of minute pearl-like points, the beauty of which has 

 probably led to the preservation of the shelh 



T, bulbosa. PI. XII. fig. 10. 



Sponge composed of a few large, irregularly shaped, and 

 somewhat depressed lobes, occasionally inclining to square, but 

 always more or less rounded ; united by a slender stem mostly 

 flattened and variable in form : papillse not large, few, penetrating 

 the surface of the matrix without order; apparently not more than 

 one or two from each lobe. Siliceous bodies of the surface like 

 those of T. cactoides, but a little less. In addition to these bodies 

 the surface is provided with triradiate and quadriradiate spicula, 

 the rays, measuring g^^i'C^ ^^ ^^ i^^^h long, arc straight, diverge 



