51 



and, therefore, to have opened externally at tlie first fjpee.arifi 

 plates. There are probably twelve of them, but onl,y..pjii;-t;t<?|j^i 

 be seen in our specimens. ■ , :.,,.,, .r-f^u,-rf. 



There can be very little utility in comparing .tMs sp«pies 

 with D. approximatiis, the only species heretofore descr^betj, 

 having eleven arms, for that species has an elonga.ted ._.qalyx, 

 four secondary radials in each scries, and four ranges, of platos 

 in the interradial areas, with four ovai-ian pores entei-jjig ,,t4ie 

 vault between each of the rays, that are continued- in.fuiTOWs 

 across the last interradial plat(>s. It can be of no service -V) 

 compare it with any species hnving a different iirni fornmla, 

 for thai alone distingiiislies it I'rohabiy it most resembles;/"'. 

 hiillntreiix whirh iia.s only ten nniis. .,...■ ,,, 



Found liy (Ico. 1\. (rreciie in the llauiilton (iroup, near 

 Charlestown. Indiana, and now in the collection of Wna. F.. E. 

 Gurley. •.■ -r' > {;• 



DOF.ATOCiviNfs r,A( HN( T r-A, n. sp. ' ■ ^ ■' 



I'Lile 111, Fkj. I'-), basal rieic; Fiij. 20, side view; Ficj. 21, sum- 

 mil riciv. 



Tliis species is fovmded upon five specimens, a medium one 

 being illustrated, and the largest having a diameter one-fourth 

 greater. Calyx low, expanded at the arms, from thi'ee to 

 three and a half times as wide as high and deeply and broadly 

 concave below. Cohnnnar pit funnel-shaped and having with- 

 in it n(,'ar the top two pentagonal raised ridges running from 

 a tubercle in the middle of eacli first radial tc. the next. a^ypit'- 

 iag. Kadial ridges merely shar|) elevations crossing the.plati^s 

 aiul Interrupted by sharp nodes at the center of each jilate. 

 Surface radiately sculpture:!. ("i)lunin rf)und, inserted into the 

 cup forme i by the basal plates and having a cinquefoil' i-ol- 

 umnar cau-il. 



Basal plates form a round cup so deeply inserted ' in ■the 

 calyx that it ri.ses higher than the calyx and ends Iti the caV 

 ity of the vault. The mouth of the cup' i.s' about oifethH-d 

 wider than the diameter of the column. Fii^st pTiraaryradtals 

 about as wide as high, sculptured in the upper part. Se'COnd 

 primary radials quadrangular, and about twice as Avide"as"ht*h. 

 Third primai'v radials expand upward to the lateral angles, 

 longer than the second, pentagonal, axillary and in «ach. 'of 



