LARVIFORM CRINOIDS 



15 



The outer border of this plate is not as uniformly convex as the others but 

 possesses a shallow concave indentation near the center in which the anal 

 plate fits. The upper surfaces of the four small oral plates bear shallow 

 indistinct concave depressions and the larger posterior plate has two some- 

 what narrower but otherwise similar depressions. 



A peculiar structure at the upper left-hand corner of the right posterior 

 radial is commonly well shown by the larger specimens, although in a few 

 smaller individuals this is definitely not developed and pentamerous symmetry 

 rules. The majority of the crinoids however are so poorly preserved that 

 its presence or absence can not be determined with certainty. The upper 

 right-hand portion of this radial bears a brachial opening of the usual type but 

 the left-hand corner is distinctly beveled and meets the next radial at a 

 position some distance below its upper surface. The inner surface of this 

 beveled corner slopes steeply inward and downward from its sharply angular 

 outer edge, apparently forming an opening that leads into the interior of the 

 calyx beneath the oral crown. A very few specimens, instead of a beveled 

 corner of this radial, show in this position a rounded projection extending 

 above the upper surface of the radial nearly to the height of the top of the 

 oral crown. Although no suture is visible there is little doubt that this pro- 

 jection is a separate plate which has been lost from most specimens. Rowley 

 did not notice such a projection of one of the radials but he suggested that 

 the beveling of the corner of the radial might represent the anal area. This 

 extension of the upper left-hand corner of the right posterior radial probably 

 represents a radianal plate which has been pushed upward and nearly out 

 of the calyx. The specimens show no indication of an anal opening and. it 

 is probable that the rectum was situated within the oral plates which were 

 capable of being opened during the life of the crinoid. 



The surface of the plates of these crinoids is unornamented and was 

 probably smooth. The specimens show minutely pitted surfaces but this 

 may be due to wear or to slight solution. 



Remarks. — This species is structurally distinct from all other known 

 crinoids. 



Occurrence. — This tiny crinoid is known only from a shale parting in 

 the Louisiana limestone at Louisiana, Pike County, Missouri. 



Genus KALLIMORPHOCRINUS 4 J. M. Weller, n. gen. , 

 Genotype Kallimorphocrinus astrus typicus J. M. Weller, n. sp., n. var. 



Monocyclic larviform crinoids of fairly perfect pentamerous symmetry, 

 copiposed of three rings of plates: (1) a low disc of anchylosed basals ; 

 (2) five, high, nearly uniformly sized radials; and (3) five petaliform orals. 



4 KaWi/wp^jos, beautifully formed. 



