THE ECHINOIDEA 



323 



aster, Desor (Fig. XLIII.) ; Homoeaster and Hypsospatagus, Pomel ; 

 Iraniaster, Cott. & Gauth. ; Lambertiaster, Gauth. ; Linthia, Merian ; 

 Moira, A. Ag. ; Moiropsis, A. Ag. ; Ornithast&r, Cott. ; Pericosmus, 

 Ag. ; Prenaster, Desor ; Schizaster, Ag. SECTION 3. PRYMNODESMINAE. 

 Spatangidae with subanal fascicle. Genera Argopatagus, A. Ag. ; 

 Brissopatagus, Cott. ; Brissus, Leske ; Breynia, Desor ; Cionobrissus, A. Ag. ; 

 Cleistechinus, Lor. ; Cydaster, Cott. ; Echinocardium, Gray ; Eupatagus, Ag. ; 

 Gaultieria, Desor ; Gibbaster, Gauth. ; Homolampas, A. Ag. ; Isopneustes, 

 Pomel ; Linopneustes, A. Ag. ; Loveuia, Ag. & Desor ; Linchophorus, 

 Dames ; Macropneustes, Ag. ; Maretia, Meoma, and Metalia, Gray ; Jfi- 

 craster, Ag. ; Nacospatangus, A. Ag. ; Neopneustes, Dune. ; Palaeotropus, 



UI 



FIG. XLIV. 



Peristomial region of S^mtangus jmrpnrcu* setMi from inside the test (after Lovon). I-V, the 

 tive ambulacra in which the vertical series are each marked a or &. 



Lov^n ; Pygospatangus, Cott. ; lihinoibrissus, A. Ag. ; Sarsella, Pomel ; 

 Spatangomorpha, Bohm ; Spatangus, Leske (Figs. XLIV., XLV.) ; Stomo- 

 porus, Cott. ; Tuberaster, Peron & Gauthier. 



FAMILY 4. PALAEOSTOMIDAE. Sternata with a pentagonal, alabiate 

 peristome, provided with five buccal plates ; a peripetalous fascicle. 

 Genus Palaeostoma, Lov^n (Leskia, Gray). 



FAMILY 5. POURTALESIIDAE. Sternata with apetalous, flush ambulacra. 

 Peristome in a deep anterior recess. Form elongate ; flat or oral surface. 

 The ambulacral plates are uniporous (Fig. XLVI.). This family includes 

 perhaps the three most perplexing of recent Echinoids ; but owing to the 

 extreme fragility of the tests their study is difficult, and owing to their 

 great variability the classification is at present unsatisfactory. The typical 

 genus Pourtalesia is the subject of an elaborate memoir by Lov6n (58). It 



