I20 ECHINOIDEA. I. 



tunately other characters are found whicli 23ro\-e to be qiiite efficieut, above all the pedicellariæ and 

 tlie spiciiles. The species mexicanus^ ni(dits, and glohjilosiis I have not seen. The other species may 

 be divided into 5 gronps, which I shall liere characterize. 



Strongylocentrotus drobacJiiensis (MiilL). Primary tubercle on all the ambulacral piates; the 

 buccal membrane with rather few piates ontside of the buccal piates, some of them thick carrying 

 pedicellariæ; inside of the bnccal piates there are more smaller, smooth or somewhat complicate piates. 

 The globiferous pedicellariæ 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 (PL XX. Figs. 25, 29). The 

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

 ribs. The tridentate pedicellariæ are very mnch 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 pedicellariæ 

 show no conspicuous peculiarities. The spicules of the ^pedicellariæ 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 pedicellariæ 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 pedicellariæ is found in the species purpuratus (Stimps.), 

 interviedius (Barn.), franciscanus (Ag.) (probably), and chloroccntrohis Brandt. In St. piirpnrahts the 

 globiferous pedicellariæ are distinguished by the imcommonly well developed articular surface (PI. XX. 

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

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

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

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

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

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

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

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

 almost none. — Of Str. intermedius 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 S laden (365. p. 434) 

 the specimen in the museum of Copenhagen must really be iiiteriuedius. There are only four j^airs of 

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

 resemble those of <!Sphærechinus~-> piilchcrriunis (PL XX. Fig. 10). The specimen in British Museum 

 has also globiferous pedicellariæ with neck and branched spicules. 



Str. chlorocentrotus Brandt is by Agassiz regarded as synonymous with drøbachiensis^ but no 

 doubt wrongly. In the description of Brandt') it is said among other things: «spinæ breves, viridesi 

 maximæ 4 linearum longitudinem vix superantes, latitudinem autem lineæ dimidiæ partis æquantes». 

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

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



I) Prodromus etc p. 64. 



