316 ECHINODERMS OF THE BRITISH ISLES 



2286 m. (" Princesse Alice ", '' Valdivia "). The three species are 

 thus distinguished : ^ 



Key to the species of Echinocyamus known from or likely 

 to occur in the British seas. 



1. Ocular pores distinctly smaller than the genital pores . . 2 

 Ocular pores as large as, or even larger than the genital pores. 



Petals small and inconspicuous . Ech. grandiporus Mrtsn. 



2. Petals small and indistinct ; peristome large 



Ech. macrostomus Mrtsn. 

 Petals well developed ; peristome small 



1. Ech. pusillus (O. Fr. Mull.) 



1. Echinocyamus pusillus (0. Fr. Midler). (Fig. 182.) 



(Syn. Echinocyamus angulosus (Leske) ; Ech. minutus (Pallas) 

 H. L. Clark.) 



Test elongate, often somewhat pointed at the anterior end. 

 Petals well developed and distinct, with ca. 6-9 pore pairs in each 



series. Genital pores distinctly 



larger than the ocular pores. 



Colour greyish or greenish. On 



preservation or w^hen hurt it 



-^ p 3 turns green, a character peculiar 



Ym. n2.-Echi'nocyamus pusillus. ^^all Clypeastroids. Scarcely 



(From Danmark's Fauna.) exceeding 15 mm. in length. 



1-2. Denuded tests from the upper (1) This species prefers a bottom 



and under side (2). 3. Specimen covered » -. i mi 



with its spines, upper side. Nat. size. ot coarse sand or gravel. Ihe 



food consists of small bottom 

 organisms, especially Foraminifera, remains of plants, and 

 bottom material (detritus) generally. It is rather much eaten 

 by fishes, especially by dab and haddock. 



The breeding season is in the summer months. The larva 

 (Fig. 183) is characterised by the body skeleton forming a 

 basket structure. Postoral and postero-dorsal rods fenestrated ; 

 no posterior transverse rod or postero-lateral arms ; no 

 epaulettes. 



In the British seas this species occurs all round the coasts and 

 is probably common everywhere on a coarse sandy or gravelly 

 bottom in shallow depths. It is elsewhere distributed from 

 Finmark to the Sound and the western Baltic, from Iceland to 



^ A full description, with figures, of the two species grandiporus and 

 macrostomus is given in the " Ingolf Echinoidea, ii., pp. 33-37, PI. XII. 



