GEKERA AND GEOUPa OP THE ECHIWOIDEA. 161 



Jaws small, stellate ; teeth superior. Perignathic processes one 

 on eaeli interradium, low, narrow, bent. Spines short and cylin- 

 drical actinally, very small and ovate-headed dorsally. 



Fossil. Miocene : Cuba. 



Hecent. W. coast of America, California, West Indies, Tucatan, 

 Panama, Plorida. 



Subgenus Monophoba, Agassiz, 1847 (genus), Bull. Soc. GSol. de 

 France, vol. iv. p. 287. Gotteaii,, 1884, Bull. Soc. Zool. de 

 France, Yol. ix. p. 340, pi. si. A. Agassiz, 1874 (subgenus), 

 Ech. ' Sassier' Exped., III. Gat. Mus. Gomp. Zool. no. 8 (1), 

 p. 13. 



Test moderate in size, discoidal, with a thin, subcircular or 

 slightly" lobed margin, may be widest posteriorly ; tumid dor- 

 sally, flat actinally. A single small lunule in the posterior 

 median line. 



Apical system central ; madreporite large, genital pores on its 

 flanks. 



Ambulacra with nearly equal petals, which are short and nearly 

 closed diatally ; poriferous zones broad ; pores of pairs unequal, 

 distant, separated by a long flexuous groove; beyond the petals 

 the pores diverge and penetrate the wide ambulacral plates. 

 Actinally, the ambulacral grooves are straight at the peristome 

 and perforated, they soon bifurcate and may ramify further out. 



Interradia narrow near the apical system, smaller than the 

 ambulacra, the posterior with a small oval oblong lunule in the 

 line of its median suture. 



Peristome subcircular. Periproct small, not far from the 

 peristome, and between it and the lunule. Tubercles abundant, 

 close, small, smallest on the flanks of the ambulacral grooves. 



Fossil. Miocene : Haut Parana and Patagonia, South America,' 



Genus Mellita, Klein, 1734, Nat. Bisp. Ech. p. 31, pi, xxi. (ed. 



Paris, 1754, p. 90, tab. xi. fig, c). Agassiz, 1841, Monoqr. 



d^EcTi. viv. et foss. livr. 2, p. 34. Gray, 1851, Proc. Zool. 



Soc. p. 3G. Michelin, 1858, Bev. et Mag. Zool. p. 358. 



Verrill, 1867, Notes on Badiata, p. 312, and 1871, p. 588. 



A. Agassiz, 1S72-4:, Bevision, pp. 140, 319, and 534. 

 Test moderate and large, very flat, slightly arched above, 

 especially anteriorly, slightly concave actinally, edge rather sharp. 



LINN. JOUKN. ZOOLOGY, VOL. XXIII. 11 



