ECHINOIDEA 331 



fascicle, running upwards on each side the periproct. Four 

 genital pores. Smaller, fragile forms, usually of yellowish colour. 

 Three species are found in the British seas. Two more species 

 are found in the Mediterranean, namely Ech. mediterraneum 

 Forbes and Ech. Morienseni Thiery (Syn. Echinocardium inter- 

 medimn Mrtsn.) ; while the latter is known hitherto only from 

 the Mediterranean, the former goes as far north as the Bay of 

 Biscay (Santander) ; there may then perhaps be a possibility of 

 its occurring also off the British south coasts, and it may be 

 desirable to include both these species in the key, referring for 

 the detailed description and figures of them to Koehler's 

 Echinodermes, Faune de France, pp. 135, 137. 



Key to the species of Echinocardiu^n known from or possibly 

 occurring in the British seas. 



1. Frontal ambulacrum deepened ...... 2 



,, ,, flush with the test .... 3 



2. The furrow of the frontal ambulacrum continuing to the apical 



system ; the pores within the inner fasciole in close, double 

 series. Larger tubercles are found scattered on the anterior 

 interambulacra above the ambitus 1. Ech. cordatum (Penn.) 

 The furrow ends abruptly at the anterior end of the inner fasciole ; 

 pores within the fasciole distant, in single series. No larger 

 tubercles above the ambitus Ech. mediterraneum Forb. 



3. No larger tubercles in the interambulacra above the ambitus ; 



labrum very short, not reaching beyond the middle of the first 

 adjoining ambulacral plates (Fig. 196, 1) 



3. Ech. pennatifidum Norm. 

 Larger primary tubercles found at least in the anterior inter- 

 ambulacra above the ambitus ; labrum generally reaching the 

 second adjoining ambulacral plates (Fig. 196, 2) . . 4 



4. Larger tubercles in all the interambulacra above the ambitus, 



rather prominent . .2. Ech. flavescens (O. Fr. Miill.) 



Larger tubercles only in the anterior interambulacra above the 



ambitus, not very prominent . Ech. Mortenseni Thiery 



1. Echinocardium cordatum (Pennant). (Fig. 194, 1-2.) ^ 



(Syn. Amphidetus [Amphidotus) cordatus (Penn.).) 



Frontal ambulacrum rather deeply sunk, the furrow con- 

 tinuing from the anterior end to the apical system ; the pores 

 within the inner fasciole very close, partly forming irregular 

 double series. Test somewhat sloping anteriorly, the greatest 



^ A good figure of a denuded test of a large Echinocardium cordatum 

 is foiond in Bell's Catalogue Brit. Ech., PI. XVI., 1 ; the figure is, however, 

 incorrect in representing the internal fasciole open in front. 



