from the Island of Malta. 1 1 3 



convex ; tubercles moderate in size ; mouth transversely ob- 

 long, situated at the junction of the anterior with the middle 

 third ; tubercles on the upper surface very small. 



Dimensions. A German type specimen. Antero-posterior dia- 

 meter 2/fl inches, transverse diameter 2^ inches, height l*fo 

 inch. 



A Maltese specimen. Antero-posterior diameter Ij 8 ^ inch, 

 transverse diameter ly 7 ^ inch, height ths of an inch. 



Description. This Urchin is well known from the admirable 

 figure in Goldfuss. Its upper surface is more convex and in- 

 flated than in the other congeneric species ; it is higher behind 

 than before, and has a blunt ridge which passes backwards from 

 the disc to the border. The antero-lateral petaloidal ambulacra, 

 ths of an inch in length, curve a little outwards, forming an 

 angle of 18; their zones contain from twenty-two to twenty- 

 four pairs of pores, separated by rather thick partitions of the 

 test. The postero-lateral areas are narrower than the anterior 

 pair, and rather more than an inch in length ; their zones con- 

 tain from twenty-eight to thirty pairs of holes, and they form 

 angles of 60. The interambulacral areas are wide and largely 

 developed in this species ; the upper plates in these areas, lying 

 between the ambulacra, support only very small perforated 

 tubercles, arranged in groups of threes and fours, and disposed 

 on all the areas; this character serves to distinguish S. Des- 

 marestii from all its congeners at present known : the small 

 tubercles on the dorsal surface are very small, and closely set 

 together. The single ambulacrum is lodged in a broad shallow 

 valley, which forms however a considerable anteal sulcus ; the 

 pores in this area are so much covered up with matrix in our 

 specimen, that we are unable to count their number. The pos- 

 terior border is truncated, and the large transversely oval anal 

 opening occupies the upper part of this region. The shelly 

 matrix entirely conceals the course of the subanal fasciole. The 

 sternal portion of the interambulacrum is slightly convex, and 

 covered with small tubercles that radiate in lines in all direc- 

 tions from a central point ; the basal portions of the anterior and 

 lateral interambulacra are covered with larger tubercles, and the 

 naked intermediate spaces indicate the trajet of the basal por- 

 tions of the postero-lateral ambulacra from the border to the 

 mouth. The mouth is situated at the junction of the anterior 

 \\itli the middle third; it is much elongated transversely, and 

 has five poriferous petals surrounding it. The apical disc itt 

 small and nearly central ; it has four genital holes and five small 

 eye-holes. 



Affinities and diffrrnices. The inflation of the test, the small- 



