EXPLANATIONS OF PLATE IX. 



Fig. I.Pal^aster sh^fferi. Ventral side, showing the ambulacral, adarabulacral 

 and marginal ranges of i)lates. 

 " 2. Pal.easter matl'tina. Dorsal side. 

 " 3. Paljeaster eucharis. Dorsal side. 



a. The madre])oriform tubercle. 

 '' 3*. PALiEASTER EUCHARIS. Ventral side. 



" 3a. '•' " An illustration of a single ray, with the centre snd bases 



of the other rays. The letters refer to the parts as follows : 

 a. Ambulacral plate ; 

 p. The pore ; 



a, a. Adambulacral plate ; 

 m. Marginal plate ; 



t, m. Terminal plate of the marginal series ; 

 o. Oral plates, of which there are five pairs. 

 '' 4. PALi^ASTER EUCHARIS. A single ray deprived of its marginal plates and flattened, 

 showing a great length of the ambulacral plates. In fig. 3a, the concavity of 

 the groove produces a shortening of the plates of the ambulacral series. The 

 letters refer to the same parts as those of fig. 3a. 

 " 5, Protaster forbesi. View of the dorsal side in outline : natural size. 

 " G. An enlargement of the lower side of a part of one ray, illustrating tlie parts as 

 follows : 



o. Oral plate ; 

 p. The pore ; 

 a. Ambulacral plate ; 

 a, a. Adambulacral plate ; 



s. Spine from anterior end of adambulacral plate ; 

 d. The limit of the circular disc. 

 '' 7. EuGASTER LOGANi. Specimen, natural size. 

 '' 8. A portion of one ray enlarged, with references to the parts as follows : 



0, 0. The oral plates, of which there are five pairs, the apices of each 



being apparently joined by a suture to the basal portions ; 

 a. Ambulacral plate ; 

 a, a. Adambulacral plate ; 

 p. Pore ; s. Spine ; 

 rf. Limit of the disc. 

 '' 9. A part of one ray of Ptilonaster princeps, showing the ranges of plates, pores, 

 spines etc. : 



d. Limit of the disc ; 



p. Pore ; 



a. Ambulacral plate ; 



a, a. Adambulacral plate ; 



7/1. Marginal plate with spine attached ; 



" 10. LePIDECHINUS RARISPINUS. 



a. The ambulacral area ; 



i, a. The interambulacral area ; 



c. r. Central range of interambulacral plates. 



