THE STELLEROIDEA 255 



FAMILY 2. LEPIDASTERIDAE. Cryptozonia with alternately arranged 

 ambulacral ossicles. Disc large ; rays comparatively short, thick, and 

 blunt. No lateral spines. The abactinal skeleton consists of closely set, 

 irregular, granular plates. Genus Lepidaster, Forbes (Fig. X.). 



FAMILY 3. TROPIDASTERIDAE. Cryptozonia with ambulacral ossicles 

 opposite or sub-alternate. Rays short, broad, arid Hat. Ambulacral 

 ossicles narrow ; adambulacral ossicles broad and thin. 

 Abactinal surface granular. Genera Tropidaster, 

 Forbes ; (?) Compsaster, Worthen & Miller. The name 

 of the type genus was suggested from the apparent 

 occurrence of a keel along the abactinal side of the 

 rays. This, however, is only due to the ambulacral 

 plates being exposed by the loss of part of the 

 granular abactinal integument. Compsaster has a 

 narrow ambulacral groove, and is bordered by 

 imbricating actinal plates ; its general characters Wenlock Limestone, 

 resemble Tropidaster, but it is insufficiently known for its affinities to 

 be definitely settled. 



FAMILY 4. LINCKIIDAE. Cryptozonia with opposite ambulacral 

 ossicles, comparatively well-developed marginal plates. Disc small, with 

 long cylindrical rays. Abactinal skeleton tessellate with granular integu- 

 mentary deposits. SUB-FAMILY 1. ROEMERASTERIXAE, with spines on 

 the marginal plates and disconnected granular plates arranged in longi- 

 tudinal series on the abactinal surface and sides of the arms. Genus 

 Roemeraster, Stiirtz. SUB-FAMILY 2. LINCKIINAE, with abactinal plates 

 devoid of internal supplementary plates. Abactinal and marginal plates 

 granulose and not bearing spines. Genera Ferdina, Gray ; Fromia, Gray ; 

 Leiaster, Peters ; Linckia, Gray; Narcissia, Gray; Nardoa, Gray; Ophidi- 

 aster, Ag.; Pharia, Gray; Phataria, Gray; (?) Arthraster, Forbes. SUB- 

 FAMILY 3. CHAETASTERINAE, with internal supplementary plates and 

 paxilliform tabulae. Genus Chaetaster, Mull. & Tr. In this genus 

 there are remarkable groups of spines borne on the ends of disc-like 

 pillars, rising from the external plates ; these are known as paxilliform 

 tabulae. SUB-FAMILY 4. METRODIRINAE, with the marginal and abactinal 

 plates covered by membrane. There are neither internal supplementary 

 plates nor paxilliform tabulae. Genus Metrodira, Gray. 



FAMILY 5. STICHASTERIDAE. Cryptozonia with opposite ambulacral 

 ossicles and contingent marginal plates. Disc small ; rays long and 

 cylindrical. The plates of the abactinal surface are large, closely packed, 

 and regularly arranged. SUB-FAMILY 1. STICHASTERINAE. The adambu- 

 lacral plates are equal, have a simple armature, and have no ridges. 

 Genera Calycaster, Per. ; Coelasterias, Verr. ; Neomorphaster, Slad. ; Stick- 

 aster, Mull. & Tr. ; Tarsaster, Slad. ; Tonia, Gray. SUB-FAMILY 2. 

 ZOROASTERINAE. The adambulacral plates are unequal, and their armature 

 is complex ; alternate plates have ridges. Genera Cnemidiaster, Slad. ; 

 Mammaster, Per. ; Pholidaster, Slad. ; Prognaster, Per. ; Zoroaster, Wyv. 

 Thorns. 



FAMILY 6. SOLASTERIDAE. Cryptozonia with opposite ambulacral 

 ossicles, and a reticulate, abaCtinal skeleton bearing paxilliform groups of 



