120 ECHINOIDBA. I. 



tunately other characters are found which prove to be quite efficient, above all the pedicellariaa and 

 the spicules. The species mexicanus, nudits, and globulosus I have not seen. The other species may 

 be divided into 5 groups, which I shall here characterize. 



Strongylocentrotus drobachiensis (Mull.). Primary tubercle on all the ambulacral plates; the 

 buccal membrane with rather few plates outside of the buccal plates, some of them thick carrying 

 pedicellariae; inside of the buccal plates there are more smaller, smooth or somewhat complicate plates. 

 The globiferous pedicellariae are highly characteristic, having a long neck provided with as well cir- 

 cular as longitudinal muscles, so that it may be retracted and stretched out (PI. XX. Figs;. 25, 29). The 

 valves have a tubular blade without lateral teeth; the stalk is tubular, its upper end with peculiar 

 ribs. The tridentate pedicellarise are very much varying as to form (PI. XX. Figs. 4, 6, 20); the small 

 teeth on the edge may form beautiful transverse series; the ophicephalous and triphyllous pedicellarias 

 show no conspicuous peculiarities. The spicules of the pedicellarise and tube feet are branched in the 

 ends (PI. XX. Fig. 12), otherwise most nearly of the bihamate form; simple bihamate spicules may also 

 be found. In the globiferous pedicellarise a dense series of spicules is often found along the outer 

 edge of the valves (PI. XX. Figs. 25, 29). 



The same peculiar form of globiferous pedicellariae is found in the species purpuratus (Stimps.), 

 intermedius (Barn.), franciscanus (Ag.) (probably), and chlorocentrotus Brandt. In St. purpuratus the 

 globiferous pedicellariae are distinguished by the uncommonly well developed articular surface (PL XX. 

 Figs. 14, 28); the stalk is strong, and seems to be compact. The tridentate pedicellariae resemble very 

 much the smaller form with the large indentations in drobachiensis (PL XX. Fig. 20), only the net of 

 meshes is a little more developed. --Of Str. franciscanus I have only seen a large, fine, dried speci- 

 men in British Museum, and unfortunately I could find no globiferous pedicellariae on it; but as the 

 spicules of the tube feet are quite identical with those of drobachiensis, I have no doubt that also its 

 globiferous pedicellariae agree with those of this species. The tridentate pedicellariae of very different 

 form; in this one specimen no less than three different forms were found corresponding to the three 

 forms figured from Str. drobachiensis. The larger ones have a strong net of meshes, the smaller ones 

 almost none. --Of Str. intermediTis a fine specimen is found in the museum of Copenhagen (received 

 from the museum in Vienna), and further I have examined a specimen in British Museum. The two 

 specimens prove, however, to be two different species, and it is not easily decided, which is the real 

 intermedius. As far as I can see from the description in Rev. of Ech. and in SI ad en (365. p. 434) 

 the specimen in the museum of Copenhagen must really be intermedius. There are only four pairs of 

 pores in each arc, and the spicules seem all to be simple, bihamate. The tridentate pedicellariae 

 resemble those of <s.Sphcerechinus pulcherrimus (PL XX. Fig. 10). The specimen in British Museum 

 has also globiferous pedicellariae with neck and branched spicules. 



Str. chlorocentrotus Brandt is by Agassiz regarded as synonymous with drobachiensis, but no 

 doubt wrongly. In the description of Brandt 1 ) it is said among other things: spinae breves, virides> 

 maximae 4 linearum longitudinem vix superantes, latitudinem autem lineae dimidiae partis aequantes. 

 (The diameter of the test is given to be i 1 / 2 "). This does not hold good with regard to drobach- 

 iensis. De Loriol (248) has lately described a species from Sitka, which he refers to Str. chlorocen- 



i) Prodromus etc. p. 64. 



