144 HEMIPEDINA. 



A. Species from the Lias. 



Hemipedina Bechei, Broderip. PI. IX, fig. 1 a, h. 



CiDAKis Bechei. Broderip, Geological Proceedings, vol. ii, p. 202. 



DiADEMA Bechei. Morris, Catalogue of British Fossils, 1st edition, p. 51. 



— — Morris, Catalogue of British Fossils, 2d edit., p. 76. 



EcHiNOPSis Bechei. Woodward, Memoirs of the Geological Survey, Decade V. Notes on 



Fossil Diademas. 

 Hemipedina Bechei. Wright, Annals and Magazine of Natural History, 2d series, vol. xvi, 

 p. 96. 



Test small, much crushed, and covered over with spines ; ambulacra with two rows of 

 tubercles ; inter-ambulacra with four or six rows of tubercles ; spines long, slender, and 

 needle-shaped, four fifths of an inch in length, with longitudinal lines on their surface. 



Description. — The test of this specimen, and the one in the collection of the Geological 

 Society, which appears to belong to the same species, is so much covered up with spines 

 and adherent matrix, that it cannot be sufficiently developed to show the details of its 

 structure. The ambulacral areas have two rows of small tubercles placed on the margins of the 

 plates ; and the inter-ambulacral areas have four or six rows of tubercles abreast. The 

 spines are long, slender, and needle-shaped ; they measure four fifths of an inch in length, 

 have a small conical head, a prominent, narrow, milled ring, and a long, slender stem, 

 which tapers gradually from the ring to the point ; their surface is finely marked with 

 longitudinal lines. 



Apnities and differences. — This species might be mistaken for Hemipedina BoioerbanMi, 

 but its test is smaller, and its spines are longer and more slender ; the head is more 

 conical, the milled ring is narrower and more prominent ; I believe it is identical with 

 Mr. Broderip's species. 



Locality and StratigrapMcal position. — This specimen has been kindly communicated, 

 together with the following species, by my friend Mr. Bowerbank, who collected it from 

 the Lower Lias at Lyme Regis, from one of the layers of marl which inter-stratifies the 

 beds of limestone. 



