434 J. W. Gregory — Australian Fossil Echinoidea. 



Ambulacra : Petals extend two-thirds of the distance from the 

 apex to the ambitus ; the lateral pairs are equal in length ; the 

 anterior ambulacrum is the longest. The petals are sharply closed 

 below ; the width of the pore area expands rather gradually to 

 the distal end of the petal, then is there closed somewhat abruptly. 

 The interporiferous areas are large, and taper slightly to the blunt 

 distal end. 



Apical system : at the apex of the test. The madreporite is raised, 

 large, and central. There are four large genital pores. Of the 

 radial (ocular) pores the right antero-lateral is very large ; those of 

 the right postero-lateral and left antero-lateral ambulacra are small ; 

 the left postero-lateral pore is not developed. 



Peristome : mouth somewhat pentagonal ; large ; the width is half 

 as much again as the length. It is situated before the centre. There 

 are no interradial actinal furrows. 



Periproct : the anus is large and almost circular ; it is close to 



o * Dimensions. 



Length ... 68 millimetres. 



Width 55 



Height 12 „ 



Mouth: width 6 ,, 



length ... ... ... ... ... 4 ,, 



« distance from anterior margin .. . ... 31 ,, 



Apical system : distance from anterior margin... 31 ,, 



Petals: anterior: length... ... ... 22 ,, 



width ... ... ... 6 ,, 



antero-lateral: length... ... ... 20 ,, 



width ... ... ... 6 ,, 



postero-lateral: length... ... ... 20 ,, 



width 6 ,, 



Distribution. — Cainozoic. Shark's Bay, West Australia. 

 Collected by Hakry Page Woodward, Esq., F.G.S. 



Affinities and Differences. — The specimen on which this 

 species is founded is unquestionably a very close ally of Laganum 

 decagonale, Less., though, as to whether it should be regarded as a 

 variety or a distinct species, I do not care to express an opinion on a 

 single specimen. It differs from that species by the elliptical and 

 somewhat pentagonal shape of the mouth, and the absence of the 

 five interradial furrows which radiate from the mouth. The British 

 Museum contains a large series of specimens of that species, but the 

 circular form of the mouth is constant ; the actinal depressions do 

 vary in degree of development, but I have not seen one in which 

 it is not quite distinct. These two characters may not improbably 

 be of specific value. 



The shape of the test differs from the normal decagonal form ; but 

 some specimens of the species have a form identical with the fossil. 



Herklots figured ' a specimen from the Java Tertiaries as Scutella 

 decagona, n. sp., Martin * referred this to Peronella decagonalis, Ag., 



1 J. A. Herklots. Fossiles de Java. Pt. IV. Echinodermes. Leyden, 1854, 

 p. 9, pi. i. figs. 6, 6a. 



• K. Martin. Die Tertiarschichten auf Java. Anhang. Revision der von 

 Herklots herausgegebenen fossilen Echinidens Java. Leyden, 1880, p. 3. 



