146 THE ATLANTIC. [cuap. 11. 
There were six specimens of a beautiful little sea-urchin, 
with a small purple body and long white serrated spines, some- 
what like those of the “ piper” of the Shetland fishermen ((%- 
daris hystrix). There is, however, an anatomical character in 
this little urchin which removes it very widely from Cidaris, 
and gives it to some of us a tremendous fancy value. The 
character is a very small one. Instead of having at the top of 
the shell a rosette of ten plates, five of them perforated to lodge 
the eyes, and five for the passage of the tubes of the ovaries, 
an additional 
this little urchin has eleven plates in the rosette 
one, large, crescent-shaped, and without a perforation (Fig. 31). 
This is entirely contrary to the usage of all the “regular” ur- 
chins of modern times; but when we 
go back to the time of the chalk, we 
find a very compact and characteristic 
little family, the SaLenrapa#, with the 
additional plate in the same position ; 
and I agree with Professor A. Agassiz, 
who has referred a specimen of a spe- 
Pe... 9 Rae cies either the same as the one we 
Ae. Showing the structure of Gredged off the coast of Spain, or close- 
pa ly allied to it, dredged by Count Pour- 
tales, in the Strait of Florida, to the chalk genus Salenia, under 
the name of Salenia varispina. 
The same haul gave a large, handsome urchin, radiant with 
mauve and white bands springing from the centre of the disk. 
This was a fine new species of the genus Phormosoma, which 
I have described elsewhere, and shown to represent the genus 
Echinothuria of the chalk, and to belong to a family which 
were supposed to have become extinct with the close of Meso- 
zoic times. 
The present form, which I will call Phormosoma uranus 
(Fig. 33), corresponds with Phormosoma placenta, a species 
taken in the Porcupine, in 450 fathoms, off the Butt of the 
