144 PROP. p. M. dttncak's eevisio;n" op the 



freely perforated by small, single pores for small, simple tentacles 

 actinally, and also more or less abactinally. Tubercles small, perfo- 

 rate, and crenulated. Open spaces or lunules may occur in tbe 

 extra-petaloid parts of ambulacra and in tbe posterior interradium*. 

 Peristome actinal, usually central ; interradial marginal plates 

 single ; perignathic girdle discontinuous; processes narrow, either 

 interradial or ambulacraL Jaws short, expanded, stellate in dorsal 

 outline, the united pyramids without braces and compasses, pro- 

 jecting over the ambulacral areas ; the teeth rarely more or less 

 vertical, mostly horizontal ; the jaws resting upon perignathic 

 processes, or having them beyond their re-entering margin ; 

 retractor muscles only. Periproct beyond the apical system, ex- 

 centric, either actinal, marginal, or dorsal in the posterior inter- 

 radium. Spheridia few, covered. 



Family Fibulariid^. 



Clypeastrid^. 



Laganid^. 



scutellid^. 



Pamily Pibulaeiid^, (subfamily) Gray, 1855, Cat. Bee. Ech, 

 Brit. Mus. pt. i. p. 27. {Amended.) 

 Small Clypeastroida with rudimentary, widely open, few-pored 

 petals ; jaws rather high ; teeth sujperior and slanting. Peri- 

 gnathic processes broad, low, one on each interradium. Inter- 

 radia small, with a single apical and a single peristomial plate, 

 continuous*. Periproct usually actinal. Slightly developed ver- 

 tical partitions within the test, actinally limiting the ambulacra 

 at their sides, radiating towards the peristome. A spheridium 

 in each ambulacrum, covered- 

 Genus Echinocyamus. 



Subgenus Scutellina (genus), Agassiz. 

 Genus Sismondia. 

 Fibularia. 

 Runa. 

 MouUnsia, 

 Rotuloidea. 



Genus Echinoctamfs, Van Phels. 1774, Brief. Leske, 1778, 



Addit. ad Klein, p. 213, Agassiz, 1841, Monogr. d'EcJi. viv. 



et foss. livr. 2, p. 125. A. Agassiz, 1874, Revision, p. 304. 



Loven, 1874, Etudes, pis. xvi. & xliv. 



Test small, thick, pyrif orm or subcircular in outline, tumid and 



* See " Definition of terms," in the last chapter of this ' Eevision.' 



