262 SALEX1A VARISPINA. 



above the other, so that there seems to be, as far as I could see. hut a 

 single pair of pores for each ambulacral plate, though near the mouth they 

 are somewhat closer, differing in this respect totally from the structure of the 

 poriferous zone of any other fossil Sitlci>i;t with which I am acquainted; for 

 in all of them we have a large number of ambulacra] plates with the pores 

 closed together. As in Salenia, the indentations of the actinostome are very 

 slight ( /'/. TIL f. '.)). The abactinal system covers nearly the whole of the 

 abactinal part of the test; the anal system is eccentric [PL IILf. 1.) There 

 is a marked difference in the size of the genital [dates, the three posterior 

 ones being much larger than the two anterior ones ; the reverse is the case 

 of the ocular plates. In the largest genital plate there is a trace of the mad- 

 reporic body, corresponding to the position of the axis assigned to it by 

 Forties. Midler, and Wright, which cuts the symmetrical axis of the sub- 

 anal plate at an angle; this is the <■; se also with the angle made by the axis 

 of the madreporic body and the first anal plate of young Echini; the position 

 of the axis passing through the anal plate has no definite relation to the 

 madreporic body. The anal opening is covered by small plates, as in other 

 Echini ( PL TIL f. //). The whole abactinal system is studded with embry- 

 onic spines , /'/. ///. /. /?). which are longest along the exterior edge of the 

 abactinal system, thus separating it most distinctly from the test. The 

 sutures between the plates are sharply cut with deep pits at the angles of 

 junction of the genital and subanal plate, and of the ocular ami genital 

 plates. The three larger genital plates have also pits in the middle of their 

 line of junction with the subanal plate. The genital openings are large. 

 placed in the middle of the plates. 

 OH' Double Head Shot Key, ;J1j fathoms. 



