389 



Family 10. ECIIINOLAMPID^, Wriglit, 1855. 



NucLEOLiDEEs (pars), Albin Gras., 1848. 

 Echinobrissidj: (pars), D'Orbiyny, 1855. 

 EcHTNOLAMPASiD.^ (pars), Grey, 1855. 

 Cassidumdes (pars), Desoi; 1858. 



The family Echl\olampid.e includes all the urchins which have petaloid or sub- 

 petaloid ambulacra ; the vent, supra-marginal, marginal, or infra-marginal, opening at the 

 surface of the test, and not into an anal valley ; the mouth edentulous ; the peristome 

 surrounded by five oral lobes, with which petaloidal expansions of the basal ambulacra 

 alternate 



The thin test has in general an oval, oblong, sub-pentagonal, or orbicular form, the 

 upper surface is convex, and depressed, elevated, or conoidal ; the vertex is usually excen- 

 tral, and situated nearer the anterior border. 



The ambulacral areas and poriferous zones form elegant leaf-like expansions on the 

 dorsal surface, and miniature petals at the base, where they develope an " oral rosette," 

 or a pen ta-phy lloid floscelle around the mouth; the leaves alternate with the prominent 

 peristomal lobes, in which the pores are arranged in crowded oblique ranks. 



The small apical disc is composed of a single imperforate, and four small perforated 

 ovarial plates ; the madreporiform body is proportionally large, extending over the other 

 discal elements ; the five ocular plates are very small, with marginal orbits. 



The vent always opens at the surface of the test, and never into a valley, as in the 

 EcHiNOBRissiD^. The opening has an oblong form ; its long diameter corresponding 

 with the transverse diameter of the test in some genera, and with the longitudinal axis in 

 others; it occupies a marginal, supra-marginal, or infra-marginal position. In some 

 existing species this aperture is closed by three thin, shelly valves, covered with tubercles ; 

 the lateral valves are larger and triangular, the central one linear, erect.* 



The tubercles are often perforated, and surrounded by sunken areolas ; in EcMnolampas 

 and Pygurus, the inter-tubercular surface is covered with a close set granulation, and the 

 tubercles at the base are much larger than those on the upper surface. 



The EcHiNOLAMPiD^ form a natural group, nearly equivalent to the Echinanthi, of 

 BreyniuSjf and which that author thus defined : 



" EcHiNANTHUs est Echinus cujus apertura pro ore est props centrum, pro ana in, vel 

 ad maryinen, longissime ah ore distantem." 



Fiyiiram omnes hujus species habent ovalem, cujus altera extremitas angustior, altera 

 latior, in qua semper apertura pro ano observatur. Ceterum pori in vertice schema 

 efformant Jloris cujusdam penta-petali, quasi acu artificiose delineatum ; et haec ratio 

 est cur huic Generi EchinatitJii nomen imposuerim. 



* 'Gray's Catalogue of the Recent Eebinida of the British Museum,' p. 35, 1855. 

 f ' De Echinus et Echiuites,' p. 59. 



