162 ECniNOlDEA. 



SPATANGIDiE (see p. 31). 



Key to the Genera of Spatangidae. 



A. Peristome nearly central 1. Neolampas, p. 1G2. 



B. Peristome excentric. 



i. No subanal fasciole 2. Schizaster, p. 1G3. 



ii. A subanal fasciole. 

 a. Some of the tubercles much larger 



than the rest 3. Spatangtjs, p. 164. 



/3. Tubercles subequal. 



i. Test highest behind 4. Echinocardium, p. 168. 



ii. Test not highest behind 5. Brissopsis, p. 172. 



1. NEOLAMPAS. 



Neolampas, A. Ay. Bull. 3fus. C. Z. i. (1869) p. 271 ; id. .Rev. Ech. 

 (1872) pp. 147 & 340 ; Wye. Thorns. Phil. Trans, clxiv. (1874) p. 745 ; 

 Duncan, J. Linn. Soc. xxiii. (1889) p. 195. 



Test prolonged posteriorly into a short blunt rostrum, and arching 

 nearly uniformly from before backwards. Ambulacra flush with 

 the surface of the test, and formed of a uniform double row of 

 single pores. Well-developed bourrelets and noscelles. 



1. Neolampas rostellata. 



Neolampas rostellatus, Al. Ay. Bull. Mus. C. Z. i. (1869) p. 271. 

 Neolampas rostellata, Al. Ag. Rev. Ech. pp. 147 & 340, pi. xvii. 

 tigs. 1-12 ; Wyv. Thorns. Phil. Trans, clxiv. (1874) p. 745, pi. lxix. 



" The single specimen procured in the 'Porcupine' Expedition, 

 which was dredged living in 690 fathoms at the mouth of the 

 English Channel, is 20 millims. in length, 16 miliims. in extreme 

 width across the ambitus, and 7 millims. in height. The outline 

 from above is not quite symmetrically oval or pyriform, the shell 

 bulging on either side somewhat irregularly towards the posterior 

 extremity. In profile, the anterior end of the test is the thinnest ; 

 the outline rises to the apex and then sinks gradually to the trun- 

 cated posterior rostrum, along the top of which it coincides with a 

 slight longitudinal ridge. The oral surface of the test also rises 

 slightly from the anterior border to produce the depression in which 

 the mouth is placed, and from the mouth it sinks towards the trun- 

 cated extremity forming the floor of the rostrum. This truncated 

 end is occupied by a deep inversion, deepest above, at the bottom of 

 which the anal orifice oj>ens. The periproct is oval, large, and plated 

 with small scales. In one specimen there is no trace of the exserted 

 anal tube described by Prof. A. Agassiz as occurring in the specimens 

 dredged by Count Pourtales in the Strait of Florida. 



" The ambulacra have all precisely the same character. Those of 

 the bivium are apparently in slight depressions. This is, however, 

 only an effect produced by the slight projection of the sides of the 

 posterior rostrum. The ambulacra are not very easily seen, the 

 pores are so minute ; by holding the shell up to the light, however, 

 they become sufficiently apparent as rows of simple pores passing 



