316 ROBERT TRACY JACKSON ON ECHINI. 



Another of the Cambridge specimens (Plate 33, fig. 11) shows four columns of plates in 

 three interambulacral areas; all five oculars are in place, four are insert as usual in the family, 

 but one is excluded from the periproct by the contact of two genitals. The oculars cover the 

 ambulacra and laterally the interambulacra in part on either side, the youngest interambulacral 

 plates being in contact with the oculars. The genitals are high, wide, and three of them have 

 three pores each; the others, two or no pores, but the pores were probably obliterated in fossil- 

 ization. Still another specimen (Plate 33, fig. 12) has all the oculars in place, and they are 

 all exsert, this as above stated being the only case seen in the family. It is a variation toward 

 the character which is the dominant one in Mesozoic regular Echini, and the youthful (sometimes 

 adult) character of all Recent regular Echini. The genitals are very wide and high and have 

 three or five pores each. Of the two specimens in Trinity College, Dublin, one has four columns 

 of interambulacral plates in an area and both show the typical character of the ambulacrum. 



The specimen in the Museum of Practical Geology Collection 16,302, shows the ambula- 

 crum and part of an interambulacrum. It is the original of Duncan's (1889) text-fig, ix, p. 206. 



Maccoya phillipsiae (Forbes). 

 Plate 33, figs. 13, 14. 



Palcchinus phillipsiae Forbes, 1848, pp. 302, 384, Plate 29, figs. 1, la; Tornquist, 1897, p. 739. 

 Palacchinus phillipsiae Roemer, 1852-'54, p. 288; Desor, 1858, p. 159; Quenstedt, 1875, p. 379, Plate 75, 



fig. 41; Klem, 1904, p. 35. 



Wrightia phillipsiae (printed by error Wrigthia) Poinel, 1869, p. xlvi. 

 Palaeechinus lihillipsiac Loven, 1874, p. 41; Duncan, 1889, p. 205. 

 Wrightclla phillipsiae Pomel, 1883, p. 115; Lambert and Thiery, 1910, p. 120. 



Form of test unknown, but probably spheroidal. Ambulacra are narrow, with two columns 

 of low plates, all of which meet the middle of the area, but are alternately primaries which meet 

 the interambulacra and occluded plates which fall far short of the same. Pore-pairs biserial. 

 The specimen is badly preserved, and in Forbes's reconstruction (my Plate 33, fig. 14) the 

 occluded plates are probably too narrow and the pores of the same too near the middle of the 

 area. There are three columns of interambulacral plates in place, and Forbes assumed five 

 columns for the area as shown in the reconstruction. This may or may not be correct. 



Forbes says, found in conglomerate under the Worcester Beacon by Miss Phillips, and 

 gives the horizon as Silurian. Forbes (1848, p. 302) considered the age of this conglomerate 

 as Caradoc, which is Ordovician (Lower Silurian), but with later study it is found to be Llando- 

 very, which is the base of the Silurian. Whether the specimen described came from this hori- 

 zon is open to doubt. A cast of the type specimen is in the Museum of Practical Geology 

 Collection 16,359. The location of the type I do not know. 



