154 



ECHINOIDEA. II. 



and the periproct, sometimes at the periproct and in the hinder lateral ambulacra at the sides of the 

 anal area; only once have I seen them in the anterior ambulacrum near the mouth. They seldom 

 occur in great numbers; 4-valved specimens may occur. Also in young specimens this kind of pedi- 

 cellarise may occur, I have found them in a specimen of n mm length. — What Koehler calls pedi- 

 cellaires gemmiformes» are evidently not the globiferous but the rostrate pedicellarise, the expression 

 «la tige calcaire de la hampe est pen eloignee de la tete not being in accordance with the globi- 

 ferous pedicellarise. 



The rostrate pedicellarise (PL XIX. Figs. 6, 15, 18, 20, 21,34) occur in very different sizes (up to 

 o-gmm length of head). The valves are wide apart, joining only with the jjoint; they are not covered 

 with a thick glandular skin like the globiferous pedicellariae. The blade is narrow, with smooth incurved 

 edges, leaving a narrow median slit; the outer part of the blade is quite open, a little widened. The 

 point is rather abruptly cut, with 8— 10 rather large serrations in the edge (in small ones only 6 such 

 serrations), those in the middle being the largest. No meshwork in the blade, but there may be in 

 the lower part a few crossbeams uniting the edges. The edges of the basal part are smooth. The 

 valves may be very strongly curved towards the point or only cpiite little so; sometimes there is a 

 distinct hump at the point (PI. XIX. Fig. 20). — The figures give an idea of how much they may 

 vary in shape. — The neck is generally well developed; the stalk is rather long, with only a small 

 « milled ring below. Also of this kind of pedicellarise 4-valved specimens may occur. They are found 

 over the whole test, but are especially numerous round the mouth and anal opening and in the anter- 

 ior ambulacrum on the abactinal side. 



The tridentate pedicellarise are generally richly developed and occur in two or three rather 

 different forms, though not very sharply distinguished, transitional forms (among the small specimens) 

 being found. The largest form (PL XIX. Fig. 29) (head up to ca. i mm long) has the valves rather wide 

 apart in about the lower half of their length; the blade is narrow and somewhat compressed, with a 

 rather sharp median keel on the outer side in the lower half, the outer part, where the valves join, 

 being more or less spoonshaped widened, and the keel disappearing gradually. No meshwork in the 

 blade, only just above the apophysis there may be a few crossbeams uniting the edges. The edge of 

 the lower, narrow part has generally a few large irregular serrations, on the outer, widened part it is 

 finely serrate. The edge of the basal part and the apophysis smooth. The holes of the outer part are 

 often large and somewhat irregular. - - The second form (PL XIX. Fig. 3) has the blade almost closed, 

 with only a small part of the point widened; this form is, however, not very sharply distinguished 

 from the first form and does not occur very commonly. Quite small specimens with the blade scarcely 

 narrowed below sometimes occur — in one specimen ( Ingolf St. 6) I found them especially developed 

 (PL XIX. Fig. 19) but I have also seen them in other specimens. The third form (PL XIX. Fig. 10) is 

 more distinct and is probably always present. The valves join in almost their whole length; the blade 

 is simply leafshaped, and the edge is straight and finely serrate; there is a slight median keel along 

 the dorsal side of the blade. This form attains almost the same size as the first one, up to ca. i" 1 '" 

 (head). All the tridentate pedicellarise have a well developed neck, and the stalk has a distinct milled 

 ring- below. 



