PLATE 1. 



Bothriocidaris archaica sp. nov. Page 239. 



Fig. 1. Lyckholm Schicht, Ordovician, Hohenholm, Island of Dago. Russia. Height 12 mm., diam. 11.2 mm. Museum 

 fiir Naturkunde, Berlin, holotype. X3.S. Two columns of high hexagonal plates in each ambulacral area, pores 

 superposed in a central peripodium. An ambulacral plate drawn in section under ambulacrum IV shows the 

 surface outline and depth of the peripodial pit, also in dotted lines the supposed thickness of the plate and position 

 of ambulacral pores. One column of hexagonal plates in each interambulacral area. The initial plate of each 

 interambulacrum rests on the two plates of the* second row of the peristome. (By an error in making my drawing 

 in Berlin, the initial plate of interambulacrum 1 rests on the third instead of the second plate of ambulacrum lb.) 

 The youngest interambulacral plates dorsally have no tubercles, other interambulacral plates have one to three 

 tubercles each (excepting the second plate in area 2 where it was probably worn off); the greatest number of tubercles 

 is near the mid-zone. In one ambulacral plate tubercles were drawn in from an adjacent plate, otherwise the tub- 

 ercles of all plates are as observed. There is no resorption of the base of the corona. There are two rows of 

 ambulacral plates on the peristome and of these, the primordial ambulacral plates la, Ha, Hlb, IVa, Vb are larger, 

 thus orienting the specimen by Loven's law. (Sec text-figs. 2, p, 54; 22, p. 70; 40, p. 80.) 



Fig. 2. Same specimen. X 5.1. Dorsal view. Oculars large, forming a continuous ring adorally, covering the ambulacra 

 and interambulacra completely; genitals small, in the dorsal angles of the oculars (pp. 42, 87). There are about 

 nine periproctal plates. (See text-fig. 162, p. 149.) 



Bothriocidaris pahleni Schmidt. Page 242. 



Fig. 3 Jeweschen Schicht, Ordovician, near Nommis, Ksthland, Russia. Height 16 mm., diam. 15.5 mm. Esthlan- 

 dischen Provinzial Museum, Reval (after Schmidt, 1S74, Plate 4, fig. la). Holotype, X about 1.6. Spines and 

 tubercles on ambulacral, hut wanting on interambulacral plates. (Compare photograph, Plate 8, fig. 1.) 



F lg. 4. Same specimen (after Schmidt, Plate 4, fig le). X about 4. Ambulacral pores superposed in a central peri- 

 podium, tubercles perforate, on ambulacral plates only. 



Fig. 5. Same specimen (after Schmidt, 1874, Plate 4, fig. Id) much enlarged. Two primordial ambulacral plates with a 

 (tooth?). 



Fig. 6. Same specimen (after Schmidt, 1S74, Plate 4, fig. lb) enlarged Dorsal view. Genitals 1 and 4 are dorsal to the 

 oculars, but genitals 2 and 3 separate the oculars and reach the interambulacra (p. 87). 



Bothriocidaris globulus Eichwald. Page 243. 



Fig. 7. Lyckholm Schicht, Ordovician, Hohenholm, Island of Dago, Russia. Height 18 mm., diam., IS. 5 mm. (after 

 Schmidt, 1874, Plate 4. fig. 2a). X about 1.6. Perforate tubercles on both ambulacral and interambulacral plates. 



Fig. 8. Same specimen (after Schmidt, 1874, Plate 4. fig. 2d). X about 4. Ambulacral plate with pores superposed and 

 perforate tubercles which also occur on interambulacral plates. 



Fig. 9. Same specimen (after Schmidt. 1S74, Plate 4, fig. 2b), enlarged. Dorsal view. Genitals all separate the oculars 

 and reach the interambulacral areas (p. 87). 



Figs. 1, 2 redrawn by .1. Henry Blake from my drawings; Figs. 3-9 copied by W. M. Barrows. The lettering and 

 orientation of all figures are mine. 



