524 SCUTELLIDAE. 



SCUTELLIDAE. 



Family Scutellidae A<,.\ss.. 1841, Mon. Scut, (emend.) 



In this family the test is reduced to its extreme flatness among Clype- 

 astroids; the outline is more or less circular, and is, unlike the Euclypeas- 

 triilac frequently perforated i>r cut at the margin, so as to form either 

 ambulacral <>r interambulacral cuts and lunules. The ambulacral furrows 

 of the actinal side are more or less branching and anastomose, spreading 

 over to the interambulacral spaces. The connection between the upper 

 and lower floors is made by partitions, radiating fan-shaped from single 

 points. The tubercles of the two sides of the test, as well as the spines 

 which they carry, differ greatly in size. The absence of rotuhe characterizes 

 the jaws of the Scutellidae; they are extremely Hat in some genera, articu- 

 lating directly upon very low auricles, and the teeth are horizontal instead 

 of being vertical as in Euclypeastridae. 



(SCUTELLA.) Eciiixakaciixius. 



Ecbinarachnius LESKE, 1778, Kl.. Add. 

 (See Bart II. p. 315.) 



Echinarachnius excentricus 



Scutella excentrica EsCH., 1829, Zool. Atl. /'/. XX. f. ?.. 



' Echinarachnius excentricus Y.u... 1846, Voyage Venus, /'/. X. 



PL XT II'. f. 1-4. 



This is the largest of the species of the genus; the test is thick; the 

 outline from above is nearly circular, elongated anteriorly, slightly truncated 

 posteriorly. The apical system is eccentric posteriorly, about one quarter 

 the distance of the vertex from the v(]'j:v of the test. The apical system is 

 large ; the posterior pair of genital openings twice ;;s far r.part as the an- 

 terior, owing to the eccentricity of the apex ; the ambulacral petals are very 

 unequally developed. The ambulacral pores of the lateral pairs of petals 

 are continued by three or four pairs diverging from the extremity of the 

 petals towards the edge, while the poriferous zone of the odd petal is con- 

 tinued by pores, becoming more and more distant, forming a distinct 

 reversed curve as a direct continuation of the gradually narrowing po- 

 riferous zone to within a couple of plates of the edge of the test. The 



