242 PHYLUM ECHINODERMATA. 



r ; Microcyphus L. Ag., r ; Amblypneustes L. Ag., r ; Goniopneustea Dun- 

 can, r ; Holopneustes L. Ag., r ; Hypsiechinus Mrtsn, r ; Grammechinus 

 Dun. and Slad., f. 



Fam. 8. Stomopneustidae. Large forms with closed auricles and 

 powerful spines. Globiferous pedicellariae without end-tooth. Stomo- 

 pneustes L. Ag., littoral, Indian Ocean, Australia. 



Fam. 9. Echinidae. Regular shell with ambulacra and interambulacra 

 of equal width ; tube feet similar. Ambulacral plates compound with 

 three pairs of pores which are arranged in arches of triplets. Peristomial 

 notches small. Coronal plates without pits or grooves, and their opposed 

 surfaces are plain. Globiferous ped. with an end-tooth and one or several 

 lateral teeth on each side. Teeth keeled. Cretaceous to recent. Pare- 

 chinus Mrtsn., pores trigeminate, primary tubercle on all the ambulacral 

 plates, globiferous pedicellariae without neck and no cross beams connect 

 the edges across the inside of the blade, numerous short greenish spines ; 

 P. miliaris Miill., North Sea, etc. Loxechinus Des. Echinus L., pores 

 trigeminate, primary tubercle on every or only on every other ambula- 

 cral plate, spines upon the whole long and strong, the actual primary 

 spines not curved at the point, globiferous pedicellariae generally with 

 the edges connected across the inside of the blade, no ocular plate reaches 

 to the periproct. E, esculentus L., primary spines short, mainly littoral 

 to about 100 fms. E. acutus Lmk., primary spines much longer than 

 secondary, to 1,350 fms. Ster echinus Koehler, Paracentrotus Mrtsn., P. 

 lividus. Fossil genera, Stirechinus, Glyptechinus, Sporotaxis, etc. 



Fam. 10. Toxopneustidae. Globiferous pedicellariae with end-tooth 

 but without lateral teeth, the edges of the blade quite coalesced on the 

 inside so that the blade is tubular, usually 1-2 oculars reach the periproct. 

 Psammechinus L. Ag. Gymnechinus Mrtsn. Toxopneustes L. Ag. (Boletia 

 Des.), littoral forms, Ind.-Pacific Oc. Tripneustes Ag. Sphaer echinus 

 Des., Channel Islands, Med., etc. Pseudoboletia Trosch. Pseudocen- 

 trotus Mrtsn. Strongylocentrotus Brdt., S. droebachiensis Miill. Antho- 

 cidaris Ltk. Parasalenia A. Ag. 



Fam. 11. Echinometridae. Globiferous pedicellariae with end-tooth 

 and one unpaired, strong lateral tooth, the edges of the blade almost 

 always connected by cross-beams across the inside ; no neck ; all littoral. 

 Pseudechinus Mrtsn. Heliocidaris Desml. (Evechinus Ver.), New Zealand. 

 Echinostrephus Ag., Indo-Pac. Toxocidaris Ag., Australia. Echinometra 

 Rond., cosmop. in warm zone. Heterocentrotus Brdt., Indo-Pac. Colo- 

 bocentrotus Brdt., Indo-Pac. 



Sub-Order 3. HOLECTYPOIDA. 



Mouth central, anus outside the apical system in the posterior inter- 

 radius, either dorsal and close to the apical system (Pygaster, Pygastrides) 

 or ventral (Holectypus, etc.). The posterior genital opening usually absent. 

 The madreporite may extend back and occupy the place of the anal area. 

 With external branchiae, apetaloid ambulacra, and a pair of pores or only 

 one pore on each ambulacral plate. The plates of the corona are not pro- 

 longed on to the peristome. With feeble jaws and vertical teeth, or 

 without these structures. Sphaeridia present. The perignathic girdle is 

 variable : it may be weak, or it may form a strong collar, the interradial 

 portions of it being wide and bent upwards and outwards from the peri- 

 sto lie internally. All the genera included in this group are Jurassic and 





