DESCRIPTION OF PHOLIDOCIDABIS MEEKI. 211 



that I have the opportunity to describe a new species which adds to the 

 known features of the genus. 



Pholidocidaris meeki, sp. nov., is from the Keokuk group, Subcarbonifer- 

 ous, of Warsaw, Illinois. The single specimen of the species is in the 

 collections of the Museum of Comparative Zoology (catalogue number 

 3070). This species is dedicated to the late Mr F. B. Meek in recogni- 

 tion of his important labors on the Paleozoic Echini. The publications 

 of Messrs Meek and Worthen on this group are by far the best and most 

 extensive done in America and are equal to the very best of European 

 works. 



The specimen of Pholidocidaris mieehi is in a limestone matrix and pre- 

 serves the original form and structure of the plates with little alteration 

 save local distortions due to fracturing. The specimen is preserved ven- 

 trally to the oral orifice in parts of the test, but is incomplete dorsally. 

 The accompanying figure, which is life size, shows the measurements of 

 the several parts. 



The plates of this species, both ambulacral and interambulacral, are 

 thin, scale-like, very irregular in form, and in both areas imbricate ado- 

 rally. On account of the thinness and strong imbrication of the plates 

 the test must have been very flexible, more so than any other Paleozoic 

 Echini studied, unless perhaps Lepidocentrus eifelianus, Miiller, which 

 has similar thin, strongly imbricating plates. These species in the flexi- 

 bility of the corona must have borne a close resemblance to the modern 

 genus Asthenosoma. 



In the ambulacrum 6 columns of plates are certainly existent, and per- 

 haps 7, but on account of local distortions this higher number is some- 

 what uncertain. Ventrally at the border of the peristome the number 

 of columns of ambulacral plates is reduced to few, apparently 4, as in 

 Lepidesthes, but the exact number was not ascertained on account of 

 local imperfections. The plates of the ambulacra are quite large, very 

 irregular in outline, and in the center of each plate is a raised mammillate 

 boss surrounded by a depressed areola. On the sides of the boss and 

 associated with the areola are two quite large pores in each plate. A re- 

 markable feature of these pores is the fact that while some are arranged 

 in a horizontal plane as compared with the test as a whole, many are 

 arranged in an inclined or even vertical plane. Thus the angles of pore 

 pairs are very various in difi^erent plates of the corona. The same con- 

 dition of irregular arrangement of pores may have existed in Pholidocidaris 

 irregularis ; but the ambulacral plates in Meek and Worthen's figure (31) 

 are so dissociated that the fact, if so, could not be there ascertained. This 

 irregularity is quite unlike anything which I have seen in other echi- 



