FROM THE CORNBRASH. 159 



secondary tubercle on its centro-sutural side (fig. 7 d), so that from the base to the 

 equator there are two rows of primary and two rows of secondary tubercles (fig, 7 a, c), 

 between the equator and the apical disc the secondary tubercles are absent, and the wide 

 miliary zone is occupied by several rows of small close-set granules (fig. 7 a, b). 

 According to the age of the test, there are from eight to ten primary tubercles and from 

 five to six secondary tubercles in each row. 



The apical disc is large (fig. 7 b), the heptagonal genital plates are much expanded and 

 perforated near their centre, the ocular plates are proportionately large, and form crescentic 

 arches over the apices of the ambulacra ; the surface of both the genital and ocular plates 

 is covered with small granules, the anal opening is central, and the rim of the aperture 

 forms a slight prominence at the vertex. 



The mouth opening is small (fig. 7 c), the peristome is decagonal, and notched into 

 nearly equal sized lobes ; from the development of the tubercles at the base of the test, 

 this region presents a much more tuberculated appearance than the upper surface, where 

 the granules of the ambulacra, and the wide miliary zone of the inter-ambulacra (fig. 7 b), 

 form a striking contrast to the tubercles which adorn the lower part of the same divisions 

 of the test at the base (fig. 7 c and d). 



Affinities and differences. — In the semi-tuberculous character of the ambulacra this 

 species resembles Hemipedina perforata, PI. X, fig. 2, and Hemipedina tuberculosa, 

 PL XI, fig. 2, but it is distinguished from both by having secondary tubercles 

 in the inter-ambulacra, which are absent in these species. It resembles Hemipedina 

 Davidsoni, PI. XII, fig. 6, and Hemipedina tetragramma, PI. X, fig. 3, in possessing 

 secondary tubercles in the inter-ambulacra, but the disappearance of the marginal tubercles 

 from the upper parts of the area shows how distinct it is from these congeneric forms. 



Locality and StratigrapUcal position. — This species was collected many years ago by 

 Dr. William Smith, and is probably the specimen from the Cornbrash of Melbury, referred 

 to in his " Strata identified by organized fossils." 



My small specimen came from the Cornbrash near Trowbridge, Wilts ; the same species 

 has been collected in the Cornbrash near Boulogne-sur-Mer. 



I dedicate this species to my excellent friend S. P. Woodward, Esq., of the British 

 Museum, as a mark of respect and gratitude for the trouble and interest he has taken in 

 the success of this work. 



Hemipedina microgramma, Wright, nov. sp. PI. XII, fig. 4 a, b, c. 



Test subpentagonal, depressed ; ambulacral areas wide, with four rows of tubercles ; 

 poriferous zones narrow and straight ; inter-ambulacral areas with eight rows of tubercles 



