338 ECHINODERMS OF THE BRITISH ISLES 



The two species may be thus distmguished : 



Posterior petals diverging, well separated ; globiferous pedicellariae 

 of one kind only, with short valves ending in two long hooks 

 (Fig. 199, 1) ; tridentate pendicellariae only 3-valved 



1 . Br. lyrifera Forbes. 



Posterior petals nearly parallel and confluent ; globiferous pedicellariae 

 of two kinds : one with long, slender valves, terminating in two 

 long hooks (Fig. 199, 2), the other with short valves with 4 

 small teeth round the terminal opening. Tridentate pedicellariae 

 occur, besides in the usual 3-valved form, also in a form with 8 

 valves (Fig. 199, 4) Br. atlantica Mrtsn. 



1. Brissopsis lyrifera (Forbes). (Fig. 200.) 



(Syn. Brissus lyrifer Forbes.) 



Test oval, arched, somewhat sloping anteriorly ; the greatest 

 height bohind the apical system. Frontal ambulacrum rather 

 deep, forming a conspicuous notch in the anterior end of the test. 

 Posterior petals somewhat shorter than the anterior, diverging, 



Fig. 200. — Brissopsis lyrifera ; denuded test, from the upper (1) and under 

 side (2). Nat. size. (From Danmark's Fauna.) 



not confluent. The peripetalous fasciole very conspicuous, 

 especially on the living animal, and forms a characteristic figure, 

 which has given rise to the specific name. The subanal area 

 encloses 4 ambulacral plates (3 tube-feet), the first of them being 

 No. 6. Globiferous pedicellariae of only one kind (Fig. 199, 1), 

 rather conspicuous, invested by a thick (in life vividly yellow) 

 glandular skin. The valves are short, ending in two rather long 

 teeth ; the stalk has some long, projecting thorns. The tridentate 

 pedicellariae of various forms, with more or less leaf-shaped valves, 



