ECHINOLAMPAS DEPRESSA. 337 



they are not closely crowded, but the secondary tubercles occupy a con- 

 siderable space round each primary tubercle; this may, however, only be 

 characteristic of the young, as in the fragments of older specimens they are 

 found somewhat more crowded ; no spines are found with any of these 

 shells and fragments, and the single whole large specimen had lost its 

 buccal and anal membranes. 



The development of Echinolampas depressa has thrown unexpected light 

 upon the affinities of the toothless Galerites and of the Cassidulidae. It 

 shows conclusively that Echinoneus is only a permanent embryonic stage 

 of Echinolampas, thus becoming allied to the Cassidulidae, and that it has 

 nothing in common with the Galerites, as I would limit them, confining them 

 entirely to the group provided with teeth. This reduces the type to a most 

 natural division, and from what we now know of the simple nature of the 

 ambulacra of all Echini in their early stages, I would not give to this feature 

 the significance which it has received, but would be inclined to unite the 

 toothed Galerites with Echinidae proper in the same sub-order, approaching 

 the Clypeastroids by the separation of the anus from the apical system, and 

 retaining the teeth and general symmetrical structure of the regular Echini. 

 I am aware that the great development of Galerites in former geological 

 periods, and the relation of the anus and test, may, on further acquaintance 

 with living representatives, entitle them to l-ank as a suborder intermediate 

 between the Echini proper and Clypeastroids. Young Echinolampas depressa, 

 measuring a trifle over 4.0 mm- , are elliptical, resembling Echinoneus, with a 

 large transverse elliptical lobed mouth {PL XVI. f. 2), the anus placed in the 

 truncated posterior extremity above the ambitus. The outline in profile is 

 almost globular {PL XVI. f. 3), truncated at the posterior extremity, where 

 the anus is placed. Each plate of the narrow ambulacral zone carries a 

 single principal tubercle {PL XVI. f. 4), surrounded by a circle of miliaries. 

 The pores are arranged in a vertical row of a single line of pores, three or 

 four for each ambulacral plate, extending from the mouth to the apex. The 

 interambulacral plates are elongated horizontally, and carry from one to 

 three principal tubercles, with numerous small miliaries arranged in circles 

 round the primaries, or irregularly scattered {PL XVI. f. 4). Seen from 

 above, the outline is elliptical {PL XVI. f. l), the madreporic body is quite 

 prominent, the large primary perforated tubercles of the interambulacral area 

 increase in size towards the actinostome, where the miliaries are also less 

 numerous. The spines are comparatively long, resembling those of some 

 of the Clypeastroids. 



