CHAP, IX. | THE DEEP-SEA FAUNA. ADT 
Twenty-six Echinideans were observed during the 
‘Lightning’ and ‘ Porcupine’ cruises off the coasts 
of Britain and Portugal at depths ranging from 100 
to 2,435 fathoms, at which latter depth the eroup 
was represented by a small variety of Hehinus nor- 
vegicus, and a young example of Brissopsis lyrifera. 
Among the Cidaridee, Cidaris papillata, LusKxn, 
occurs in enormous numbers over hard ground, at 
depths from 100 to 400 fathoms. This species has 
a very wide range, inhabiting an apparently un- 
broken belt from the North Cape to the Strait of 
Gibraltar, and then passing into the Mediterranean. 
This is a variable form, within narrow limits of 
variation. ‘The southern specimens gradually pass 
into the form,—it can scarcely be called a variety,— 
which is the type of Lamarck’s species, C. hystrix. 
Cidaris affinis, PHtLiprt, is very common in the 
Mediterranean, especially along the African coast. 
I think this pretty little form must for the 
present be considered distinct. The body spines 
are bright scarlet, and the long spines, in marked 
specimens, are brown, banded with red or rose, so 
that it is a singularly pretty object. 
The genus Porocidaris and the three species of the 
family Echinothuride, and their interesting relations 
to fossil forms, have already been considered ; but 
even these are scarcely more suggestive of early 
times than two genera of irregular urchins, one 
dredged off the coast of Scotland, and the other at 
the mouth of the English Channel. 
The first of these is Pouwrtalesia, one species of 
which, P. jeffreysi, has already been figured and 
described (p. 108). According to the classification of 
