100 MESOZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



minute perforated tubercles having crenulated bosses. The tubercles increase in size as they approach the peristome. 

 Interspaces filled with small tubercles and microscopic granulations. Both peripetalous and lateral fascioles are clearly 

 defined, peripetalous fasciole decidedly bent inward between the anterolateral and posterolateral petals and somewhat 

 less so between the other petals. Apical system situated in the center or somewhat anterior to the center of the dorsal 

 surface, small, depressed, having the four genital plates perforated and separated by five small radials. Peristome 

 transversely elliptical, situated near the anterior margin. Labruni prominent. Periproct somewhat elongated ver- 

 tically and situated near the top of the posterior truncation. 



Related forms. — L. tumidula, the only other species of this genus hitherto described from 

 the American Cretaceous, is so unlike L. variabilis that detailed comparison is unnecessary. 

 Localities. — Onemile Run, Pontotoc, and Tippah County, Miss. 

 Geologic horizon. — Ripley formation, Upper Cretaceous. 

 Collection. — Field Museum, Chicago (P 10457). 



