336 ECHINODERMS OF THE BRITISH ISLES 



ambulacrum, within the fascicle, distant, in regular single series. 

 Test rather flattened above, scarcely rising posteriorly, gently 

 rounded at the anterior end. No larger tubercles (spines) in the 

 interambulacra above the ambitus. Labrum very short, not 

 reaching beyond the middle of the first adjoining ambulacral 

 plates (Fig. 196, 1). The globiferous pedicellariae, which are 

 usually not very numerous, are mainly like those of cordatum, 

 but the stalk is without free projecting rods ; the tridentate 

 pedicellarise (Fig. 195, 5) are very characteristic, the valves with 

 strongly serrate edges. (This form, which is very conspicuous, 

 reaching a size of ca. 2-5 mm. length of head, has given rise to 

 the specific name j^ennatifidum ; other smaller forms of tridentate 



Fig. 198. — Echinocardium pennatifidum ; naked test, from above. Nat size. 

 (After Koehler, Faune de France.) 



pedicellaria?, with more simple, leaf-shaped valves, occur in both 

 this and the other species of the genus.) The triphyllous pedi- 

 cellariae (Fig. 197, 3) are finely serrate along the whole edge of 

 the blade. Reaches a large size, up to 70 mm. length. 



Biology apparently the same as that of cordatum ; very 

 common within the tide limits at the Channel Islands (Herm). 

 Development unknown. Appears to form hybrids with Ech. 

 ftavescens. 



In the British seas this species has been found, though no- 

 where in larger numbers, on the south, west, and north coasts, 

 and down to Durham on the east coast ; it has also been taken 

 on the " Porcuj^ine " Bank (165 m.). It is elsewhere distributed 

 from the coast of Norway (Haugesund) to the Mediterranean, 



