II. Arbeiten von speciellerem Character. 4. Echinoidea. 211 



serrated, somewhat flattened, differing radically in external appearance from the 

 spines of the Triplechiuidae thus far known. 



Spatagocystis gen. nov. Test ovoid, actinal region flattened, the anteriorly promi- 

 nent actinal keel extending to form an anal snout, the abactinal region of the test 

 regularly arched , the anterior and posterior extremities rounded , the actinal 

 groove sunken. In the apical system, the genital plates connected, placed in the 

 trivium, separated from the bivium by the intercalated interambulacral plates. 



Echinocrepis gen. nov. This genus has, like Pourtalesia, a sunken actinal groove, but 

 the other features of the test differ entirely from those of the species thus far de- 

 scribed in this family. There is no anal snout, the anal system though forming a re- 

 entering pouch much as in Pourtalesia is situated on the actinal side as in Cyste- 

 chinus. Seen in profile the test is pyramidal, the apical system is placed about one- 

 third the length of the test from the anterior end ; the anterior part of the test forms 

 a regularly inclined surface sloping rapidly from the apex to the ambitus with 

 sharply rounded corners ; towards the actinal surface and at the median line of 

 the lateral anterior ambulacrum on the upper part of the test , the actinal groove 

 forms a comparatively slight depression on the actiual surface of the anterior edge 

 of the test, but owing to the gradually sloping sides of the edge of the actinal 

 groove, extending from the flat actinal anterior part of the test, and taken in con- 

 nection with the flat sloping test of the anterior extremity and its deep re-entering 

 angle when seen from above, it forms, when seen from the anterior extremity, a 

 groove deeply cut out of the test. As seen from above the anal keel forms a slight 

 arch from the apex to the anal extremity. The median line of the anterior lateral 

 ambulacra is slightly re-entering, forming a deep indentation in the anterior out- 

 line of the test as seen from above. 



Ur echinus gen. nov. At first sight this genus appears closely allied to Neolampas, 

 of which it has the general outline . The pos terior region of the test forms as 

 in that genus the hood protecting the anal system. The difference in the pro- 

 portion of the plates composing the ambulacral and interambulacral areas as well 

 as the structure of the actinostome at once distinguish it from Neolampas. It has, 

 like the Pourtalesiae , large high plates forming the ambulacral zones differing 

 little in height from the adjoining ambulacral plates. It has a nearly circular acti- 

 nostome like that of Cystechinus slightly sunken below the level of the actinal sur- 

 face. The abactinal system is disconnected; two of the genital plates go with 

 the trivium, the others with the bivium. 



Cystechinus gen. nov. This genus has the facies of Ananchytes , and is also closely 

 allied to Galerites. It has, like the latter, the test made up of plates of nearly 

 uniform size in the different interambulacral areas, and large plates like the Anan- 

 chytidae in the ambulacral areas, and a slightly sunken actinostome. In this genus 

 the actinostome is less eccentric than is usual in Spatangoids , and in this respect 

 one of the Galeritic features of the genus is strongly marked. The anal system is 

 just below the ambitus, but it has the abactinal system of the Ananchytidae.n 



Argopatagus gen. nov. This genus is closely allied to Homolampas; it has like it 

 a subanal fascicle, but no peripetalous fasciole; the primary tubercles both on the 

 ambulacra and interambulacra are largest and most crowded at the ambitus ; they 

 become less numerous towards the abactiual pole , and smaller though numerous 

 towards the actinostome. The odd anterior ambulacrum is not sunken, but like the 

 others flush with the test. The structure of the ambulacra is similar to that of Ho- 

 molampas, but on the abactinal surface the ambulacral plates are larger in compa- 

 rison with the interambulacral ones than in that genus ; they are all more or less 

 hexagonal. The primary tubercles are more numerous in the odd anterior ambu- 

 lacrum on the abactinal side. The structure of the apical system is like that of 



14* 



