Anatomy of the Temnopleuridae. 113 



inner or adoral suture which reaches the adoral suture of the 

 primary just noticed, as it passes upwards. The lower or 

 adoral component plate («) is a large primary, and it occupies 

 most of the compound plate. This is a very usual arrange- 

 ment, and is similar to that of Echinus and its allies ; but 

 the inner suture of the dcmi-plate differs in the nature of its 

 curve, and it is not simply oblique, as in Echinus proper. 



The triple pairs of pores are more in arcs in Salmacis (fig. 4) 

 than in TemnoijJeurus (figs. 2, 3), and in both genera the 

 pores of pairs are much wider apart on the inside of the test 

 than they are in the peripodia (compare figs. 2 and 3). 



Mespilia. (PI. XI. fig. 5.) 



The same arrangement of plates and pairs of pores as is 

 seen in Temnopleurus and Salmacis occurs, slightly modified, 

 in Mesjn'lia globulus. The compound plates of this species 

 are decidedly low and broad, and more so than in the genera 

 just alluded to. The pairs of pores are in triplets, the pairs 

 being close vertically. The middle pair of pores of the triplet 

 (h) is close to the ambulacro-interradial suture in a rather 

 broad, low, demi-plate, whilst the aboral pair (c) is nearly 

 vertical to the adoral pair {a). Both of these pairs are in 

 primary plates, the adoral being in the largest. As in the 

 other genera the pores of a peripodium are much closer than 

 their continuations within the test. 



Microcyphus. (PI. XI. figs. 1, 6-12.) 



There are some very remarkable and, in my experience, 

 unique structural characters about the ambulacra of Micro- 

 cyphus zigzag, Agass., which appear to be due to the growth 

 in thickness, externally and internally, of the plates and to 

 the very oblique paths of the canals of the pores. Blocking 

 out of the ends of component plates occurs, and some plates 

 which are perfectly visible on the inside of the test are not 

 seen on the outside, and they have been hidden by the con- 

 tinuous superficial deposit of test material. Moreover, parts 

 of the component plates of compound ones are sometimes sepa- 

 rated from their sutures in a very unusual manner (fig. 1). 



On looking at the ambitus of a specimen (fig. 6) the low 

 broad ambulacral plates, which are broader superficially than 

 within, are noticed to have an adoral pair of pores (a) nearer 

 the median line of the ambulacrum than the other pairs, 

 which are oblique and close to the ambulacro-interradial 

 suture J a number of plain tubercles and miliaries are upon 



