512 ROTULA AUGUSTI. 



digitations are Formed without exception as marginal cuts, forming at first 

 mere indentations of the outline of the nearly circular test. The three pos- 

 terior median interamhulacral notches are the first to appear. Subsequently 

 the two anterior interamhulacral cuts appear (first on the lower side), and 

 the median ambulacra] cuts of the posterior pair of ambulacra much as they 

 are formed in Encope. 



The petals are long, narrow, open at the extremity ; the interporiferous 

 space is of uniform width, broadest in the odd petal, and narrowest in the 

 posterior lateral pair of petals. The poriferous zones are broad in old speci- 

 mens, broader than the median space ; the poriferous zones extend as isolated 

 pairs of pores nearly to the edge of the test. In large specimens, measuring 

 from 60""" to TO""", the structure of the poriferous zones becomes peculiar. 

 The inner row of pores is the largest in young specimens, and is united to 

 the outer row of smaller pores by an indistinct groove. In the larger speci- 

 mens this indistinct furrow is completely pitted, for the outer part of its 

 length, by small pores, nearly as large as the outer pore, extending from the 

 outer pore to within a short distance of the inner row of pores (about one 

 third tin' width of the poriferous zone); this structure is well figured by 

 Agassi/, in his Monographic des Scutellcs. hut is not referred to in the text. 

 It gives to the petals a peculiar aspect, the poriferous zones appearing, as it 

 were, to be formed of narrow, sharply cut lines, commencing at a distance 

 from the inner row of pores, and extending to a minute outer row of pores. 



The tuberculation of the abactinal surface is homogeneous ; the spaces 

 between the primary perforated and crenulated tubercles are closely packed 

 by miliaries. The apical system is small, compact, pentagonal, with four 

 large genital openings in the middle of the anterior sides of the pentagon. 

 There are irregular ridges running to the apex and centre of the sides of the 

 apical system, which are not riddled by the holes of the madreporic body. The 

 ocular pores are small, placed at the outer angles of the apical system. The 

 whole system is raised above the level of the abactinal part of the test. 

 standing out prominently from the apical extremity of the petals. 



On the actinal side the tuberculation is coarser ; the tubercles adjoining 

 the ambulacral furrows are small, and the miliaries are more distant and less 

 numerous than on the abactinal surface. The mouth is small, circular ; the 

 ambulacral furrows deep, separating into two branches immediately near the 

 mouth, and forking again about half-way towards the edge, so as to send one 

 branch into each digitation of the margin of the test. The anus is rather 



