442 A. Olsson—JYew Genus of Palceechinoidea. 



Aet. XXXVIII. — Description of a new Genus and Species of 

 Palceechinoidea /* by Axel Olsson. 



Lepldechinoides gen. nov. 



Shape subspheroidal with five ambulacrals and five inter- 

 ambulacral fields. Ambulacrum consisting of two columns of 

 alternately arranged plates imbricating aborally. Each of the 

 ambulacral plates pierced in the middle by a pair of pores set 

 close together. In addition each ambulacral plate is pierced 

 on the extreme ventral surface by a single pore situated on the 

 adjacent ends of the plates. Interambulacrum composed of six 

 columns of adorally imbricating plates. Adambulacral plates 



Fig. 1. 



Lepidechinoides ithacensis Olsson. 



Fig. 1. Side view of specimen enlarged three diameters. 

 Nos. 1, 2, 3, 4, 5, 6, indicate number of column. V, 2', 3', 4', initial 

 plates. 



slightly smaller than the second column of plates and perforated 

 near ambulacral edge. The interior plates of the interambu- 

 lacral series more or less hexagonal in shape, except those on 

 the extreme ventral surface, which are small and scale-like. 

 Spines small and striated, dilated at the base. 



* The writer is indebted to Prof. H. S. Williams for the many kind sug- 

 gestions in the preparation of this paper. 



