264 THE FOSSIL ECHINOIDEA 



Length 67 millim., breadth 61 millim., height 26 millim. 



Locality. Nari series, Oligocene of Sind. Mal-Mohari, west of Jungshahi. 

 Survey-number G ^^-g-. 



Dimensions of the Series of Forms of Echinolampas coming within the species 

 Echinolampas discoideus, d'Archiac. 



Length. Breadth. Height. Length to Length to 



millim. millim. millim. breadth. height. 



1. Form 89 83 36 1 to 093 1 to 0-41. Type. 



2. Form 78 74 35 1 to 0-94 1 to 0-46. Type. 



3. Form 113 105 54 1 to 093 1 to 0-4. Var. a. 



4. Form 126 117 53 1 to 0-93 1 to 042. Var. a. 



5. Small specimen . 59 53 19 1 to 0-98 1 to 0-32. Var.0. 



6. Another .... 67 61 26 1 to 0-9 1 to 0-38. Var. y. 



8. EcHiNOLAMPAs PLACENTA, Buncan & Sladen. Plate XLII, Figs. 1-3. 



The test is large, nearly as broad as long, very depressed, nearly circular in outline, 

 but slightly nipped-in and produced behind, and slightly flattened over the infra- 

 marginal periproct. The margins are rounded rather sharply, and the highest point of 

 the test is slightly excentric in front at the apical disk. There is a sharper slope in front 

 than behind the apical system, and some flattening occurs over the anterior ambulacrum. 

 But in spite of the flattening, the anterior margin is more swollen than the posterior 

 (Fig. 3). The actinal surface has a gradual slope to the central peristome. 



The apical system is flat and rather large, the madreporic body occupying the 

 space between the four well-marked generative pores, and extending behind the line of 

 the two posterior so as to separate the radial (ocular) plates of the posterior ambulacra. 

 The ambulacra come to visible points beyond the madreporite, and the radial (ocular) 

 plates are rather large. The ambulacra (anterior part of odd one is missing) are long, 

 extend close to the margin, are open widely, are flush with the test, and are broad with 

 comparatively narrow poriferous zones, which are unequal in the same ambulacra to 

 some extent. 



The narrowest ambulacrum is the anterior, and the longest and broadest are the 

 postero-lateral ambulacra. The pores are rather large, the outer one elongate comma- 

 shaped, and the inner nearly circular in outline ; and the costse, moderately broad, 

 have a row of miliaries on them. The pairs narrow towards the distal end. The 

 antero-lateral ambulacra, very wide apart, have the anterior poriferous zone nearly 

 straight, except close to the marginal end, where there is a slight curving backwards 

 and obliquity of the pores ; the posterior zone is curved and sinuous, for distally the 

 curve alters and the concavity is backwards ; and this is the larger zone of the two. The 

 posterior ambulacra have the anterior poriferous zone more bent than the other, but it 

 is the shorter of the two. The peristome is small, pentagonal, broader than long, and 

 widely open. The floscelle is well developed, the phyllodes are distinct, the antero- 

 lateral in grooves, and there are some extra plates, and most of the pores are double. 



