61 
useful to give a short summary of what has hitherto been made 
known about the matter. 
In the „Ingolf 44 Echinoidea I. (1903, p. 162) mention is made 
of a pair of specimens from Norway, which „combine to a curious 
degree the characters of both E(chinus) esculentus and acutus, var. 
Flemingii, so that it is quite impossible to decide with certainty 
to which of these species they belong, and the supposition of their 
being hybrids between the two species seems very obvious 44 . Un- 
Fig. 1. 
Supposed hybrid of Echinus esculentus and Ecli. acutus. Nat. size. 
fortunately both are naked tests so that several of the more im- 
portant specific characters cannot be observed, and thus full cer¬ 
tainty cannot be reached. No figures were given in the work 
quoted, so I have thought it desirable to figure one of the specimens 
at this occasion (Fig. 1). It will be seen that the shape is quite 
that of esculentus, while the tuberculation is more like tliat of 
acutus var. Flemingii, the tubercles only being somewhat smaller 
than is generally the case in this form. The colour is a combina- 
