562 THE ANIMAL KINGDOM. 



and the test therefore cannot have been firm. Aristotle's lantern present. Anus 

 exocyclic only in Cystoddaris. Basal plates pierced by three to fi>e, radials by 

 two, pores. Spines small as a rule, and restricted to interambulacra. 



2. Desmosticha (= Regulares, Endocyclica] : of spheroidal or flattened circular 

 form. All ambulacra and interambulacra of equal length. Anus endocyclic. 

 Mouth central. Complex manducatory organs (Aristotle's lantern). Subdivided 

 into 



(a) Entobranchiata = Cidaridae : devoid of external gills. Auricular arch 

 not complete and interradial. Ambulacral and interambulacral plates continued 

 on to peristome ; pores in straight rows ; pore plates primary and subequal. 



(b) Ectobranchiata : external gills present. Auriculae extend over the radii. 

 Interambulacral plates not continued on to peristome. (Saleniidae, Echinothuridae, 

 Arbadadae, Diadematidae, Echinidae.} 



3. Clypeastroidea (= Exocyclica in part) : shield shaped, often flattened. 

 Mouth central, with manducatory organs. Dorsal portion of five ambulacra 

 petaloid. Ambulacra of great breadth. Anus exocyclic. (Clypeastridae, Scutel- 



4. Petalosticha (= Exocyclica in part, Spatangoidca] : more or less heart- 



shaped. Mouth more or less excentric ; no manducatory organs. Anus exocyclic. 



Ambulacra petaloid, and anterior one often unlike the other four. Subdivided into 



(a) Cassidulideae : oval, with mouth central or subcentral ; no petaloid 



ambulacra or all petaloid. (Echinoneidae, Cassidulidae^) 



(&) Spatangideae : mouth excentric and transversely elongate ; a labrum ; 

 four ambulacra, petaloid as a rule; fascicles often present. ( Collyritidae, Anan- 

 chytidae, Spatangidae?) 



General anatomical account, Kohler, Annales Mus. Nat. Hist. Marseilles, i. 

 1883. See also A. Agassiz, ' Revision of Echini,' Harvard Mus. Catalogue, No. vii. 

 pt. iv. or iii, 1872-74; Id. Challenger Reports, iii. 1881. 



Test) Zittel's Palaeontologie, Abth, i, Palaeozoologie, i. 1876-80. 



Classification of Desmosticha, Bell, P. Z. S. 1881. 



Cyanosoma urens, an Echinothurid, and its poison apparatus, Sarasin (C. F. 

 and P. B.), 'Ueber einen Lederigel,' &c., Z. A. ix, 1886. Pourtalesia, Lov^n, 

 Kongl. Sv. Ak. Handl. xix. No. 7, 1883. 



Pedicellariae, cf. lit, p, 194, and note, p. 558, ante. Sphaeridia, Ayres, Q. J. M. 

 xxvi. 1886. 



Structure of teeth, Giesbrecht, M. J, vi. 1880. 



Nervous system, Prouho, C. R., 102, 1886; Romanes, ' Jellyfish, Starfish, and 

 Sea-urchins,' Internat. series, 1885, cap. x.; Id. and Ewart, Ph. Tr. 172, 1881, 

 P- 835- 



Compound eyes in an Urchin (Diadema ?), Sarasin (C. F. and P. B.), Z. A. viii. 

 1884. 



Vascular system, points in dispute, Carpenter, Q. J. M. xxiv. 1884; xxv, 1885. 



Echinochrome or blood-colouring matter, MacMunn, Q. J. M. xxv. 1885. 



Pluteus of Dorocidaris, Prouho, C. R. 101, 1885. 



