POURTALESIA MIRANDA. 345 



Mr. Pourtales. It forms a valuable link in our appreciation of the affinities 

 of Spatangoids proper with Spatangoids in which the mouth is not labiate. 



Test thin, bottle-shaped, when seen from above ; vertically truncated an- 

 teriorly, the anterior apex corresponding to the abactinal pole, in profile 

 the outline is rectangular, convex below ; the posterior actinal part of the 

 test projecting far beyond the anus like a proboscis ; the posterior ex- 

 tremity cut out to receive the pit occupied by the anal system. Seen 

 endways, the test is heart-shaped ; mouth elliptical, not labiate, sunken in 

 a deep actinal groove ; abactinal and actinal plastrons narrow, elongated, 

 formed of closely packed tubercles. Tubercles few' in number, with large 

 scrobicular circle carrying long curved spines slightly fan-shaped at the 

 extremity. Smaller spines spatulate ; four genital openings. Ambulacral 

 pores extending as simple rows from the apex to the actinostome. Ambula- 

 cral suckers pointed. 



Pourtalesia miranda 



! Pourtalesia miranda A. Agass. 1869. Bull. M. C. Z., I. p. 272. 



PL XVIII. 



Seen from above (PL XVIII. f. 3), the outline is bottle-shaped, the 

 neck being the posterior extremity. At the base of the neck the test car- 

 ries a deep pit, surmounted at its exterior extremity by a rostrum projecting 

 from the test, and under this, at the bottom of the pit, is placed the anus 

 (PL XVIII. f. 6, 7). Seen in profile, the anterior extremity is almost verti- 

 cally cut oft* (PL XVIII. f. l), the test arching regularly from the apical 

 system to the rostrum, where it is abruptly cut off", forming a regular curve 

 to the posterior extremity, this extends beyond the anal system like a 

 snout thickened at the end (PL XVIII. f. 5), surmounted at its extremity by 

 an accumulation of minute tubercles, colored dark violet, which carry no 

 spines. The lower surface is convex, regularly arched from the posterior to 

 the anterior extremity (PL XVIII. f. l). The posterior pair of ambulacra 

 extend on both sides of an elongated plastron to the base of the snout-like 

 prolongation, where they curve sharply upwards, and run close to the abac- 

 tinal part of the test (PL XV III. f. l). to the abactinal system situated 

 almost at the summit of the nearly vertical anterior extremity, along a 

 marked wedge-shaped ridge, extending from the apical system into the ros- 

 trum protecting the anus. The anterior pair of ambulacra take a similar 

 course in the opposite direction, but curve more regularly (PL XVIII. f. J,), 



