454 PSEUDOBOLETIA. 



somewhat distant. Median ambulacra! region flanked by two vertical rows 

 of larger tubercles ; the median space is occupied by smaller tubercles, form- 

 ing in the oldest specimen examined six horizontal rows of tubercles, the 

 exterior rows somewhat the largest. On the coronal plates the tubercles 

 of both areas are closely packed, forming horizontal lines in the ambu- 

 lacral space, and somewhat oblique lines in the median interambulacral 

 space. Miliaries distant. In the interambulacral space there are from six 

 to seven vertical rows in the largest specimens examined; the row placed 

 one third the distance from the median line is somewhat more prominent 

 than the others. The rest of the coronal plates is thickly covered by sec- 

 ondaries and comparatively only a few miliaries. The lower surface is 

 quite flattened. Actinostome has sharply marked cuts. Anal system large. 

 with prominent plates; genital ring quite narrow opposite madreporic geni- 

 tal, which is much larger than the remaining genital plates. Ocular and 

 genital plates closely covered with small tubercles. Genital openings large, 

 placed near exterior, almost at the very extremity of the pointed genital 

 plates. Two ocular plates reach the anal area ; they are rectangular and as 

 large as the adjoining genitals: ocular pore prominent. Auricles thin, slen- 

 der, with large foramen and low connecting ridge. Actinal membrane 

 moderately covered by small longitudinal plates, with ten extremely promi- 

 nent buccal plates. 



( STRONG YLOCENTROTUS. ) Psfxdoboletia. 



Pseudoboletia Tkosch., 1869. Verhdl. d. Nat Ver. £ Eheinl. n. West. 



Professor Troschel called my attention to the peculiar arrangement of 

 the pores of some species of Echini which I had referred to Boletia, and for 

 which he proposed the name of Pseudoboletia. The species of this genus 

 have the general facies of Toxopneustes, the spines are comparatively longer, 

 and the plates of the buccal membrane are thickly covered by small spines. 

 The general arrangement of the primary tubercles is like that of Toxop- 



