ECHINOIDEA. I. 147 



on all the ambulacral piates. The scrobicular areas join 011 the actinal side as far as to the ambitns. 

 On the abactinal side the primary tubercles decrease very iimch in size. The secondary tubercles form 

 at the ambitus a tolerably distinct longitudinal series inside of the primary one, but they are con- 

 siderably smaller than the primary tubercles. There are generally a couple of small tubercles just 

 inside of each are of pores. Besides numerous small tubercles are found on the actinal side, a few 

 ones on the abactinal .side. 



The interambulacral areas (PI. XV. Fig. 17). The primary tubercles form a strong, uninter- 

 rupted longitudinal series, but the scrobicular areas do not touch each other on the actinal side; on 

 this side they are only little larger than the ambulacral primary tubercles, on the abactinal side con- 

 siderably larger. In large specimens they decrease only ver>' little in size towards the apical area, in 

 smaller specimens, on the other hånd, they decrease very much in size, so that the whole abactinal 

 side gets a strikingh' smooth and naked appearance, the secondary tubercles being here also very few. 

 The actinal side is closely set with secondary tubercles forming a distinct longitudinal series inside of 

 the primary one, and the tubercles of this series may be almost as large as the primary ones. Out- 

 side of the primary series the secondary tubercles are scattered, not placed in longitudinal series. The 

 miliary tubercles are generally few in number and little conspicuous, so that they do not deprive the 

 abactinal side of its smooth character. 



The apical area (PI XVI. Fig. 8) is most frequently somewhat raised, especially the inner edge. 

 The form of the ajsical piates show no peculiarities; there is generally a circle of tubercles along the 

 inner edge. In some specimens two pores may be found in one or a couple of the genital piates. 

 The periproct is rather large, covered by numerous small, irregular piates, among which the central 

 plate mav be distinct; the piates nearest to the anal opening are a little lengthened, thick, irregularly 

 club-shaped. On specimens in alcohol only these knobs are seen nearest to the anal opening, so that 

 it looks as if the other part of the periproct were naked (Koehler 226. p. 94); in dried specimens the 

 whole area is distinctly seen to be covered with small piates. — lu the description by Dan i el s s en 

 the curious expression occurs: the membranous portion (periprocte) is closely covered with round cal- 

 careous vessels ; this, no doubt, is owing to the faet that an erratum in the Dani.sh text, Kalkkar in 

 stead of < Kalkkorn , has passed into the English text, which has thus got the meaningless expression 

 <'calcareous vessels.> in stead of calcareous grains;. 



The buccal membrane coutains numerous large, thin, highly perforated calcareous piates 

 (PL XXI. Fig. 27) ; those inside of the buccal piates are much smaller and almost without holes 

 (PI. XXI. F~ig. 18. a). There is a slight indication of a radiate arrangement of the inmost piates. Very 

 few or no bihamate spicules in the buccal membrane. No spines on the buccal piates; only in larger 

 specimens a few pedicellariæ are found outside the buccal piates. The gills with the usual irregular 

 calcareous piates and a few bihamate spicules. 



The length of the .spines is very vars-ing, as is seen from the noted measures; thus in two 

 specimens of a diameter of 45""" the longest spines in one specimen are 22"'"', in the other 43'"'". In 

 some specimens the spines are even longer than the diameter of the test, as is especialh' seen in the 

 statements of Koehler. All the specimens of Koehler seem to have been long-spined; among 

 those from the Ingolf onh' a few long-spined specimens are found (especially from st. 78), in most 



19* 



