1^6 ECHINOIDEA. I. 



Psanimechinus Ag. (emend.) 



(S\nonynis: Lytccliinus Ag., Psilcchimix Ltk., Scliizcchimis Pomel.) 



Pores trigeniinate; primary tubercle on all the ambulacral plates. Slits of the test rather deep. 

 The buccal membrane with numerous plates forming a more or less distinct plate-covering. In the 

 globiferous pedicellaria; the blade is not much lengthened. The spicules dumb-bell-shaped, form no 

 border round the globiferous pedicellarise. The spicules of the tube feet bihamate, not branched. The 

 spines of a middle length, greenish. 



Species: Psaiiinicc/i. varicgatns (Lamk.), scniitubcrculatus (Val.), vcrrucitlatiis Ltk. 



Distribution: The eastern and western coasts of tropical America; the Indian Ocean. Lit- 

 toral forms. 



Gymnechinus n. g. 



Pores trigeniinate; primary tubercle on all the ambulacral plates. Slits of the test small. The 

 buccal membrane, with the exception of the buccal plates, contains no fenestrated plates at all. In- 

 most in the edge of the mouth more or fewer irregular, needle-shaped spicules are found; also numer- 

 ous bihamate spicules are found, especial!)- nearest to the edge of the mouth and the outer edge. In 

 the globiferous pedicellarite the Ijlade is not much lengthened. The spicules of the globiferous pedi- 

 cellaria; arcuate or slightly dumb-bell-shaped, form no border. Smaller, sliort-spined forms. 



Species: Gyvnirc/i. Robillardi (Loriol), danilcyciisis iWoods)'). 



Distribution: Mauritius, Australia. Littoral forms. 

 Toxopneustes Ag. (emend.). 

 (vS\-nonyiii: Bolctia Desor.) 



Pores trigeniinate; primary tubercle only on ever\- other ambulacral plate. Slits of the test 

 deep. The buccal membrane with numerous fenestrated plates most of which are quite imbedded 

 in the skin. In the globiferous pedicellarice the blade is much lengthened. The spicules in the globi- 

 ferous pedicellaria; are t\-pically dumb-bell-shaped and form a thick, white border round the outer 

 edge of the \-alves; in the tube feet branched, bihamate spicules are found. Large, flat, shorl- 

 spined forms. 



Species: T. fiilcoliis (Lamk.), rosrns Ag., clcgaiis Diklerl. 



Distribution: The Indo-Pacific Ocean. Littoral forms. 

 Tripneustes Ag. (emend.) 

 (Synonym: Hipponoi' (iray.) 



Pores trigeminate; primary tubercle only on ever}- third or fourth ambulacral plate. The pore 

 areas very broad, so that the pores form three separated vertical series; in the small individuals the 

 pores are jilaced in the usual maimer in short arcs. The buccal membrane with numerous fenestrated 

 plates most of which are (|uitc imbedded in the skin. vSlits of the test rather deep. In the globiferous 

 pedicellaria; the blade is not much lengthened; the pedicellari;e upon the whole small and darkh- 

 pigmented. The spicules in the globiferous pedicellariie are typically dumb-bcll-shajicd; tlie\- 

 fonii no border. Tlic l)ihamalc spicules in the tube feet arc not branched. Large, high, shorl- 

 spined forms. 



'I CoiniJ. abovt p. no. 



