

KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 58- NIO 9. 17 



Besides this form the usual triphyllous pedicellariae are found (Pl. V, Fig. 11) 

 and small tridentate, 0,i mm length of head (Pl. V, Fig. 7). Ophicephalous pedi- 

 cellariae are not found. 



This species is so well characterized by the combination of characters described 

 and by the exceptional feature of the five-valved pedicellariae that there can be no 

 doubt of its specific validity, even though there is only a single, not very finely 

 preserved specimen in hand. 



12. Echinodiscus auritus Leske. 



Pl. V, Figs. 1, 5, 9, 10. 



Lobophora aurita. L. Agassiz. 1811. Mouogr. des Écbinod. vivans et fossiles. II. Des Scutelles, p. 70, 



Tab. 14, Fig. 3. 

 ~Echin@äiscus auritus. A. Agassiz. 1873. Revision of the Echini, p. 531, Pl. XIII c, Figs. 1—2. 



» » Diiderleln. 1902. Ecliiiioidea ... Amboina u. Thursday IsL, p. 722, Taf. L.\Y, 



Fig. 1-3. 

 De Meijere. 1914. Siboga-Echinoidea, p. 138, Taf. XIX, Fig. 366—368. 

 » » H. L. Clark. 1914. Hawaiian a. o. Pacific Echini. The Clypeastridae, p. 71, 



Pl. 125, Figs. 9 — 10. 



Two specimens, labelled only West Australia, 1911; one of them measnres 130 

 mm in length, 120 mm in width, the other, which is very much broken, measures 

 110 mm in length. The shape of both specimens agrees with that figured by Dö- 

 derlein (Op. cit., Pl. LXV, Fig. 1). It may be mentioned that both specimens 

 have a very distinct, white-tipped anal proboscis. 



While De Meijere mentions small tridentate and triphyllous (?) pedicellariae as 

 occurring in this species, H. L. Clark states these pedicellariae to be bidentate and 

 biphyllons. (The figure 368, Tab. XIX of De Meijere would also seem to be a 

 bidentate pedicellaria.) The two specimens in hand have no bi valved pedicellariae; 

 they are all three-valved. This remarkable difference in the pedicellariae would 

 appear to indicate that there are two different species included in the Echinodiscus 

 auritus as presently circumscribed. Whether these will perhaps prove to correspond 

 to the forms distinguished by the older authors as Echinodiscus (Lobophora) bifissa 

 and aurita must remain an open question as yet. In any case specimens with 

 bi-valved pedicellariae should be critically examined and compared with such as 

 have three-valved pedicellariae. 



The tridentate pedicellariae are quite conspicuous, reaching a size of 0,4 mm 

 length of head. They are rather different in shape. In one form (Pl. V, Figs. 1, 5) 

 the valves are strongly serrate in the outer part, with no serrations in the lower 

 part; they recall the valve figured by Clark, which has, however, only some small 

 serrations at the point. The other form (Pl. V, Fig 9) looks more like the one 

 figured by De Meijere. The triphyllous pedicellariae (Pl. V, Fig. 10) are rather 



K. Sv. Vet. Akad. Handl. Band 58. N:o 9. 3 



