16 



PALEor.XKrsTKS (KISTATrs. 



gins ; minute distant miliaries are irregularly scattered between them, and 

 extend over the whole test : the abactinal tubercles are larger and some- 

 what more crowded in the interambulacral spues adjoining the petaloid 

 portion of the lateral ambulacra. In the odd ambulacrum these large tuber- 

 cles are limited to the abactinal part of the interambulacrum, where they are 

 closely crowded together, and. carrying, as they do. larger spines, form a BOrt 

 of tuft near the abactinal pole. The larger spines adjoining the petals protect 

 them, somewhat as in other Spatangoids, by arching over them. The remain- 

 ing spines of the abactinal surface are finely serrated, short, straight, resem- 

 bling at first sight the spines of the regular Echini {Fig. 8). They stand 

 out in all possible directions from the test, and have not a general trend, as 

 is the case in all Spatangoids. The spines of the actinal side are somewhat 

 curved, much longer, spoon-shaped at the tip, finely striated, but not serrated 

 ( Fig. .-')• except near the ambitus, where the spines become straighter and 

 Bhorter. The spines of the actinal surface trend all in one direction. A 

 transverse section of one of the actinal spines (F/>/. pi) shows the general 

 structure of Spatangoid spines. The large open cells of the central portion 

 of the shaft, characteristic of these spines, are not a common feature among 



Spatangoids, where the central space is generally hollow ; these larg 

 recall the structure of the central part of the spine in Diadematidae and in 

 Arbaciadac. The miliaries carry minute Bilk-like Bpines of similar structure 

 with the larger ones ; and either large pedicellariffi, with rather -tout stems 

 ( Fig. //land large beads {Fig. tf), similar to those of Spatangus proper, or 



