278 



ECHINODERMATA— ECHINOZOA 



PHYLUM IV 



Pedina Ag. Amh narrow, poriferous areas wide. Both areas with two 

 vertical rows of small, perforate, primary tubercles. Upper Jura. 



Pseudopedina Cotteau. Like the preceding, but with larger primary 

 tubercles, which are present in the Ämb near the ambitus only. Upper Jura. 



Micropedina Cotteau. Amb with several, and lAmb with numerous vertical 

 rows of very small primary tubercles. Cretaceous. 



Leiopedina Cotteau (Chrysomelon Laube). Test large, melon-shaped. Amb 

 long, straight, very broad. Poriferous areas broad, pore-pairs triserial, and 

 almost horizontal. Plates very numerous, low, broad, Compound. Tubercles 

 small, piain, finely perforate, in two distant vertical rows. lAmh broad, with 



Pio. 390.. 



Stomechinus lineatus (Goldf.). Coral Rag; Sontheim, Würtemberg. A, Side-view of test, i/j. B, Portion 



of Retinal surface. 



two rows of tubercles similar to the ambulacral, and with intermediate 

 granules. Eocene. 



Stomechinus Desor (Fig. 390). Distinguished from Pedina by its wider 

 Amb, and imperforate, non - crenulate primary tubercles. Secondary 

 tubercles and granules often present. Jura and Cretaceous. 



Codechinns Desor. Tubercles very small, piain, irregularly distributed. 

 Cretaceous. 



Polycyplms Agassiz. Jura. Astropyga Gray. Recent. 



Family 4. Echinothuriidae Wyville Thomson. 



Ambulacral plates Compound. Coronal plates very thin, imbricate. Primordial 

 interambulacral plates in basicoronal row. Base of Corona not resorbed. Oculars 

 insert, often separated from the genitals by interspaces. Genitals more or less split 

 by secondary sutures. Periproct leathery but partially plated. Peristome with many 

 rows of ambulacral plates only. Lantern inclined. Radial peristomal and somatic 

 muscles. Stewarts organs present. Jurassic to Recent. 



This family is represented by several living and two extinct genera, the 

 latter being known only by fragmentary specimens. Pelanechinus Keeping 

 is found in the Upper Jura, and Echinothuria Wood ward in the Upper 

 Cretaceous of England. Phormosoma Wyv. Thomson (Fig. 371, A) and 

 Asthenosoma Grube. Recent, occurring chiefly in depths below 1 00 fathoms. 



