SUMMARY. 



175 



covered with fine longitudinal lines and small indistinct tubercles. The genus occurs 

 in the Inferior Oohte. One British Oolitic species (Vol. I, p. 450). 



Genus 8.— Pedina, A(jassiz (Vol. I, p. 171). 



Test very thin, nearly equally depressed on the upper and under surfaces. Ambu- 

 lacral areas narrow, with two rows of small primary marginal tubercles, Interambulacral 

 areas wide, with two rows of perforated primary tubercles, and two to four rows of 

 secondary tubercles extending from the peristome to the circumference. Bosses of 

 tubercles uncrenulated. Poriferous zones wide; pores trigeminal, and arranged obliquely. 

 Apical disc small. Oral opening small, slightly notched. The genus is met with in the 

 Oolitic strata. Two British Oohtic species (Vol. I, pp. 173—176, 459). 



Family IV.— ECHINIDJ3, WrigU (Vol. I, p. 183). 



Test generally thin, globular or depressed ; plates numerous. Ambulacral areas one 

 third the width of the interambulacral, bearing two or more rows of tubercles. Inter- 

 ambulacral areas with large plates, sometimes perforated at the angles, sometimes 

 marked by depressions on the line of sutures, sometimes sculptured with irregular figures 

 in relief, sometimes microscopically plaited, and generally bearing many small imperforate 

 tubercles arranged in rows. Poriferous zones narrow or wide ; pores unigeminal, 

 bigeminal, obliquely trigeminal, or in three vertical rows. Spines short, subulate, and 

 sculptured with fine longitudinal lines. Oral opening large or small. Peristome often 

 pentagonal, feebly or strongly notched. Jaws present. Apical disc small. The family 

 ranges from the Oolitic to the existing period. Pamily represented in the British Oolitic 

 strata by four genera : Glypticus, Magnotia, Polycyphus, and Stromechinus. Ten 

 British Oohtic species. 



Genus 9, — Glypticus, Agassiz (Vol. I, p. 185). 



Test thick, small, spherical, or subconoidal. Ambulacral areas narrow and straight, 

 with two rows of marginal tubercles arranged in linear series. Interambulacral areas 

 bearing two rows of well-developed imperforate and uncrenulated tubercles on the under 

 side, and irregularly formed prominences on the upper surface. Poriferous zones narrow ; 

 pores unigeminal. Oral opening wide. Peristome decagonal, slightly notched, and 

 unequally lobed. Genus found in the Oolitic strata. One British Oolitic species 

 (Vol. I, p. 186). 



