LOVENKCHINIS. 329 



peristoraal border, the plates are primaries only, with pore-pairs uniserial, a typical character 

 of this zone in the genus. The intorambulacra are somewhat imperfect and a number of plate- 

 are restored in area A as indicated by dotted lines. With this restoration (a space for which 

 exists in the specimen), there are four columns of plates in the area. Moth ambulacral and 

 interambulacral plates in part bear small secondary tubercles. This specimen is of impor- 

 tance, as the one from which Duncan (1889, p. 200, text-fig, viii) described the structure of the 

 ambulacrum as that of Palaeechinus ellipticus. He was perhaps misled by the original label, 

 which reads Palaechinus ellipticus M'Coy, but since studying M'Coy's type of ellipticus in 

 Dublin, I know that this was a mistake of identification. The structure of the ambulacrum 

 and the interambulacrum in this specimen differs essentially from that of P. ellipticus (Plate 

 29, fig. 2; Plate 30, figs. 8-10; p. 308, and footnotes, pp. 303, 320). 



A specimen from Hook Head, Ireland, in the Science and Arts .Museum, Dublin, has the 

 same structure as that last described, with four columns of denii- and occluded ambulacra!, 

 and four columns of interambulacral plates. The size is about the same as that of the Hel- 

 sington Barrows specimen. 



The specimen from Llysfaen in the British Museum Collection E 3,432 (Plate 35, fig. 6; 

 Plate 36, figs. 7, 8) I ascribe to this species with much hesitation, as it differs so much in M/C 

 and superficial appearance from those previously described. However, as it has the same 

 structural character as typical lacazei, it is placed in this species. The test is large, rounded, 

 and somewhat elliptical, but its actual height is apparently greater from the dorsal dislocation 

 of plates. It is a superb specimen, finely preserved. Width of ambulacrum at the mid-zone, 

 10 mm., interambulacrum, 30 mm. From these measurements the circumference would be 

 about 200 mm. and diameter about 64 mm. The height as estimated is about 72 mm. and the 

 width, if completed on the left side, about 68 mm. The ambulacra at the mid-zone have four 

 columns of plates which are narrow demi- and wide occluded. Pore-pairs lie near the next 

 adjacent interambulacra. About eight demi-plates at the mid-zone equal the height of an 

 adradial. The ambulacra are high, rounded, and laterally bevel over the ambulacrals on the 

 adradial suture. In ambulacrum B ventrally, as shown in the specimen (not in the dra\\ ingi, 

 within about 10 mm. of the base, the ambulacral plates are all primaries crossing the half- 

 areas, and pore-pairs are uniserial, as in the ventral area of other species of the genus. Then- 

 are four columns of plates in an interambulacral area at the mid-zone and throughout mo-t of 

 the vertical extent of the area, as shown in area A. The same is true of area I, and a third area 

 on the reverse side. In area I ventrally (not shown in the drawing), there is a single plate 

 representing the left of the two plates of the basicoronal row, three plates in the second row, 

 and four plates in the third row, as in text-fig. 25, p. 70. The surface of the plates is high, 

 rounded, and covered with small secondary tubercles. A single genital plate dorsally in place 

 is high, wide, with three genital pores. Three other genitals are more or less displaced, and 



