254 Mr. H. J. Carter on Deep-sea 



Warborough, Berkshire, forwarded to me by the Rev. R. 

 St. Pattrick, in company with a full spicular complement of 

 the fossil Geodia termed (I. c.) Geodites haldonensis, in great 

 abundance, which appears to have been the specimen in parti- 

 cular enclosed in this flint. 



Thus the Gummina would seem to have grown about the 

 Geodia before the latter became imbedded for fossilization ; 

 while it is curious that among the deposits of heterogeneous 

 sponge-spicules in the Upper Greensand of Haldon Hill, 

 I should have happened to select the very spicules for the 

 representative of Geodites haldonensis that are, with the ex- 

 ception of those of the supposed Gummina, exclusively present 

 in the powder of the Warborough flint. 



Thus it would a priori appear that, by going to the interior of 

 flints, we may be able to find out the exact spicular complement 

 of each species whose spicules are heterogeneously mixed up 

 in the spiculiferous deposits of the Greensand. 



But, on the other hand, the presence of seven existing 

 species together, as found in the deep-sea specimen to which 

 I have above alluded, shows how we may be defeated in this 

 inquiry. 



EXPLANATION OF THE PLATES. 

 Plate XIII. 



All the spicules in Plates XIII. and XIV. are flesh-spicules, and, to 

 show their sizes relatively, all, with the exception of fig. 32, a, Plate 

 XIV., have been drawn on the scale of l-12th to l-6000th inch. Eig. 

 32, a is drawn on the scale of l-12th to l-1800th inch. 



Fig. 1. Halichondria inerustans, Bk, equianch orate, three views : a, 

 lateral, J, anterior, and c, posterior views, respectively ; ddd, 

 shaft; eeee, anterior arm ; ffff, lateral arms; gg, falx of 

 anterior arm ; hhh h, falces of lateral arms ; i i, tubercle, here 

 linear. 



In this instance the shaft is alate on each side, above and 

 below, as seen in b and c. 



N.B. The anchorate of Halichondria inerustans is figured and 

 described in detail especially to enable the reader to compre- 

 hend the following forms of this spicule, which are so modi- 

 fied, that they would be almost unintelligible without a key of 

 this kind. 



Fig. 2. Guitarrajimbriata, n. gen. et sp., natural size. 



Fig. 3. The same, magnified two diameters : a, apical vent, surrounded 

 by a fringe of long spicules ; b, root ; c, smaller vents on the 

 surface ; d, portion of surface en prqfil, more magnified to show 

 the structure of its villous surface. 



Fig. 4. The same, three views of the anchorate : a, lateral view, 

 b, anterior, and c, posterior view (all fringed on their inner 

 aspect) ; d, fringe ; e, tubercle ; f, falx. 



Fig. 5. The same, embryonic form of this anchorate. 



