ECHINOIDEA. II 



and not cup-shaped at the upper end; the neck is well developed. The blade is coarsely dentate along 

 the whole edge; the lower part of the blade is very narrow, forming a small tube. The basal part is 

 not distinctly developed, the articular surface is broad aud well developed. Some larger forms, very 

 similar to these, might also be termed triphyllous pedicellarke, but from analogy with the Ech.grandi- 

 ponts described below, in which species there can be no doubt that these are tridentate pedicellarke, 

 the larger ones may also be termed tridentate in pusillus. (PI. XII. Fig. 23). The blade is more elong- 

 ated than in the triphyllous; the edge is serrate, the serrations on the point being the larger, often 

 considerably larger than in the one figured; the basal part as in the triphyllous. Size ca. o - o8 — o-oo,"" 11 . 



The buccal membrane does not contain any plates or spicules; the same holds good for the 

 internal organs. The genital organs are much branched aud interlaced, but apparently not anastomos- 

 ing, forming a broad ring. The axial organ shows some distinct swellings. The madreporic plate has 

 on the inside a deep and large impression for the axial organ and the ampulla. 



The largest specimen of this species seen by me is 15""™ in length. The size 9 lines (20 mm ) 

 given in Zoologia Danica (loc. cit.) seems hardly correct. It is very variable as regards the shape of 

 the test. This has caused older authors ( L. Agassiz, Forbes) to distinguish a number of species 

 based almost exclusively on differences in the shape of the test, viz. among the recent forms: E. pu- 

 sillus, angulosus aud tarentinus, besides a number of fossil species from the Tertiaries. Philippi (op. 

 cit.) has first pointed out that these differences are unreliable for specific characters, since all the dif- 

 ferent forms may be found among specimens from the same locality. Philippi and all the later 

 authors after him (except Forbes) therefore regard all the recent forms from the European seas as 

 one species including also several of the fossil species . I quite agree with this, and might further 

 add as synonymous the E. hispidulus Forb. and E. ovifonnis Forb., both from the Crag, examples of 

 the same shape as these occurring likewise among the recent specimens. — Forbes further disting- 

 uishes no less than six different varieties of Ech. pusillus, all of which, he agrees, may be taken in 

 one localitv at the present day . It is evident that all these forms cannot rank as varieties , they 

 represent merely individual variations in the shape of the test. - Perhaps the specimens from the 

 Fasroe Islands mav rank as a distinct variety. On comparing them with specimens from the Kattegat 

 and the Mediterranean I find that the number of pores is upon the whole a little smaller in the former 

 (cotnp. the tables given below, p. 34); but it is no constant feature, specimens from the Fseroe Islands 

 occurring with as large a number of pores as is generally found in the specimens from the Kattegat. The 

 shape of the test is upon the whole more elongated than in the specimens from the Kattegat; also, the 

 primarv spines are generally somewhat less serrate than those of the typical form, sometimes even quite 

 smooth ones mav be found. — The specimens from the Limfjord may also be distinguished as a local 

 form, remarkable for the close tuberculation. — The Mediterranean form I am unable to distinguish as a 

 separate varietv: they closely agree with the specimens from the Kattegat. The same holds good for 

 the specimens from the Azores. 



This species was taken by the IngolF at St. 86 (Brede Bugt, Iceland, 7 dead tests). At the 

 Westmanoer, Dr. A. C. J oh an sen has taken 4 dead tests (30 fathoms); in the Zoological Museum is 

 found further an old dead test from Reykiavik. These are, so far as I know, the only specimens of 

 Echinocyamus pusillus known from Iceland; it thus seems that the species does not live there now, 



