394 Miscellaneous. 



sure through the external surface, but they occupy its very centre ; 

 each grain being separately encysted by the cartilaginous matter of 

 the skeleton, the whole being surrounded by a thick coating of the 

 same substance. The author describes at length the mode in which 

 this curious structure appears to have been built up, and illus- 

 trates his descriptions by highly magnified drawings of the manner 

 in which the grains are built into the fibrous skeleton. Spicula were 

 of rare occurrence in this specimen ; when observed they were im- 

 bedded in the external coating of the cartilaginous fibres ; they are 

 short and comparatively thick in proportion to their length, decrea- 

 sing very slightly from the middle to near the points, and are termi- 

 nated acutely but somewhat abruptly. 



The third species is the Spongia fragilis of Montague, or Duseideia 

 fragilis of Johnston's manuscript. It is massive, variable in form, 

 of a dull ochreous yellow colour, and has the surface asperated by 

 the projection of fibres, which contain numerous grains of sand im- 

 bedded in a manner similar to those described in treating of the last 

 species. There are also other fibres which are tubular in their struc- 

 ture, containing few or no grains of sand, but an abundance of spi- 

 cula remarkable for their great variety in form and size. 



No spicula were found in the fleshy matter of the sponge, but a 

 considerable number of round or oval bodies were present, which pre- 

 sented every appearance of being cytoblasts. 



The author concludes his paper by some observations on the pre- 

 sent state of our knowledge of the structure of the Spongida, and 

 notices certain changes that will become necessary in their systema- 

 tical arrangement when our information regarding their structure is 

 more matured. 



The paper was illustrated by drawings of the Sponges, and the 

 various descriptions of spicula contained in their structures. 



MISCELLANEOUS. 



NIGER EXPEDITION. MR. FRASER. 



A letter has just been received, by the Zoological Society, from 

 Mr. Fraser, the naturalist to the Niger expedition, dated from the 

 mouth of the river Nun, West Africa, August 14, 1841. In the first 

 part of his letter Mr. Fraser alludes to a collection of specimens 

 which he had formed during his passage out, and forwarded to 

 England. The collection consists of three mammals, twenty-eight 

 reptiles, fifty birds, upwards of thirty fishes, and about forty boxes, 

 bags, &c, containing insects and shells. The letter contained some 

 interesting facts relating to the habits and localities of several dif- 

 ferent species, and the writer expressed a hope that they would not 

 be regarded as a specimen of what might be expected, as he had 

 purposely abstained as much as possible from using his materials for 

 preparing specimens until his arrival at the Niger. 



Little Auk In the 'Annals and Mag. of Nat. Hist.' for December, 



I perceive a notice by Mr. Townsend of the occurrence of Mergulus 



