48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



Subgenus MEPYGURUS Pomel 



Mcpy gurus Pomel, 1883. Class, meth., p. 65. Type specias, Py gurus michclini 

 Cotteau, i84g=Pygurus dcprcssus Agassiz in Agassiz and Desor, 1847, by 

 subsequent designation, Lambert and Thiery (1921, p. 356). 



Description. — This subgenus includes all those species of Pygurus 

 that have a low, broad test, with a central or slightly anterior apical 

 system, slightly depressed and not broadened phyllodes with three 

 of four series of pore pairs in each half -ambulacrum, and with the 

 first pore pairs in a phyllode near the edge of the peristome. 



Range. — Jurassic (Bajocian to Oxfordian). 



DESCRIPTION OF TYPE SPECIES 

 PYGURUS (MEPYGURUS) DEPRESSUS Agassiz 



Plate 2, figures 2-5 ; text figure 25 ; chart 3, figure a 



Pygurus depressus Agassiz in Agassiz and Desor, 1847. Ann. Sci. Nat., Zool., 



ser. 3, vol. 7, p. 162. 

 Pygurus michclini Cotteau, 1849. £ch. foss., L'Yonne, vol. i, p. 70, pi. 5, fig. 7. 



Material. — Three specimens were studied in the Museum of Com- 

 parative Zoology at Harvard, one in the U. S. National Museum, 

 and four in the ficole des Mines in Paris, including two specimens 

 figured by Cotteau (1869, pi. 31, figs. 1-3). 



Shape. — Large, up to 84 mm. in length, shape variable, in some 

 specimens length greater than width, in others less than width; 

 anterior margin often blunt, posterior margin often pointed, greatest 

 width central or posterior to center ; test low, flattened, with greatest 

 height at apical system or anterior to it ; adoral surface depressed, 

 pulvinate, with interambulacra inflated, ambulacra depressed. 



Apical system. — Central or slightly anterior, tetrabasal, genital 

 2 large, extending posteriorly, separating posterior genital plates 

 (text fig. 25), posterior ocular plates in contact. 



Ambulacra. — Petals equal, broad, closed, long, extending almost 

 to margin; interporiferous zones very wide, tapering distally ; porif- 

 erous zones wide with outer series of pores elongated into broad 

 slits, inner pores slightly elongated transversely, pores conjugate; 

 poriferous zones tapering distally. 



Periproct. — Inframarginal, longitudinal, tear-drop shaped with 

 apex pointing adorally ; in slight, flat groove extending one-half 

 distance from periproct to peristome. 



Peristome. — Slightly anterior, pentagonal, width slightly greater 

 than height in some specimens, less than height in others. 



FlosceUe. — Bourrelets strongly developed; phyllodes long (chart 3, 



