760 



PROCEEDINGS OF THE NA TIONAL MUSEUM. 



the radials. Ambulacra ver}^ large, three-fourths the length of the 

 theca, with flat sides sloping down to the depressed median groove. 

 Length of each ambulacrum about 45 mm., greatest width about 9 or 



10 mm. There are about 25 ambulacral 

 grooves in 10 mm. Interambulacral 

 areas deeply and angularl}- indented. 

 Deltoids very long and narrow. 



RemarA'i^. — In the structure of the 

 ambulacra, the deep interambulacral 

 areas, and form of basal half, the new 

 species agrees ver}- nearl}^ with P. sul- 

 cati/s Roemer. It difl^'ers, 

 being twice as large as 

 the average adult speci- 

 men of that species, and 

 in the more important 

 particular that its apical 

 lono-er and more attenuate. The deltoids also 



Fig. 2.— Basai. view of Pentremites 

 maccalliei in outline, restored to 

 probable normal form. 



end i,^ 



however, in 



JVr\ 



Fig. 3.— Section of 



PENTEEMITES MAC- 

 CALLIEI ACROSS AN 

 AMBULACRAL FUR- 

 ROW, SHOWING THE 

 VERY SLIGHT CON- 

 VEXITY OF THE 

 SLOPES ON EITHER 

 SIDE OF THE MEDI- 

 AN GROOVE. 



are correspondingly longer and narrower. The re- 

 cently described J\ foA^l" has similar ambulacra and 

 equals P. maccalUei in size but difl'ers decided!}' in 

 having flat instead of deepl}' cora-ave interambulacral 

 spaces. Finallv, /■*• ohesus L^'on, an even larger species, while ])eing 

 similarly pentalobate in cross section, has ver}^ diflferent ambulacra, 

 these being biconvex in transverse contour, as in 1*. godoni De France 

 and its allies. As the new species is based on a single mature example, 

 nothing can be given regarding the developmental changes. 



Formation and locality. — The specimen w'as found b}- Dr. S. W. 

 McCallie in the Bangor limestone in an old lime quarry in Nickajack 

 gulch, a short distance below the coke ovens at Cole City, Georgia. 



Holotype.—G^i. No. 35689, U.S.N.M. 



«Ulrich, U. S. Geol. Surv., Prof. Paper No. 36, 1905, pi. vii, figs. 5 to 9. 



