230 ACROSALENIA. 



A. Species from the Lias. 

 Acrosalenia minuta, Buckman. PL XV, fig. 3 a, b, c ; PL XVII, fig. 2 a, b, c, d, e. 



Echinus minutus. Buckman, in Murchison's Geology of Cheltenham, 2d ed., p. 95. 



Acrosalenia crinifera. Wright, Annals and Magazine of Natural History, 2d series, 



vol. xiii, p. 168, pi. 12, fig. 1. 

 — Forbes, in Morris's Catalogue of British Fossils, 2d edition. 



Additional species of Echinodermata. 

 — minuta. Oppel, die Jura Formation Englands, Frankreichs, und des 



sudwestlichen Deutschlands, p. 1 10. 



Test circular, depressed ; ambulacral areas very narrow, with two rows of microscopic 

 tubercles placed at some distance apart on the sides of the area, those on the right side 

 alternating with those of the left; inter-ambulacral areas with two rows of primary 

 tubercles, from nine to ten in each row, so disposed that the test appears, from the 

 narrowness of the ambulacra, to possess only ten rows of tubercles, nearly equidistant from 

 each other ; spines long, numerous, and hair-like. 



Dimensions. — Height, three twentieths of an inch ; transverse diameter, six twentieths 

 of an inch. 



Description. — This beautiful little urchin has been long known to our local geologists, 

 as it was obtained in great numbers when cutting through the Oxynotus bed of the Lower 

 Lias in the formation of the Birmingham and Bristol Railway ; it has often been a 

 palseontological puzzle, for although a few specimens have been found in a tolerable state 

 of preservation, still, for the most part, the test is so much injured by pyrites, that it 

 requires a good lens, and much patient study, to make out the details of its structure. I 

 lately found a very good specimen in the Oxynotus shales near Lansdown, which forms the 

 subject of fig. 2, PL XVII, and is the most perfect example I have seen. In my ' Memoir on 

 the Lias Echinodermata,' I figured and described this species as Acrosalenia crinifera, 

 Quenst., but my friend Dr. Oppel, of Stuttgart, having kindly sent me the type of 

 Quenstedt's species, I am satisfied, from the comparative shortness of the spines of our 

 urchin, that it is distinct from that form, and have, therefore, restored its original specific 

 name, minuta. 



The test is nearly circular, and is more or less depressed ; the ambulacral areas are 

 extremely narrow (PL XVII, fig. 2 d), with two rows of minute marginal tubercles, not much 

 larger than the common granulation of the test ; these tubercles are placed in each row at 

 some distance apart (fig. 2 e), and the tubercles of the one side alternate with those of 

 the opposite (fig. 2 b); between these two rows of tubercles there is a narrow, zigzag line 

 of granulations ; the tubercles are very uniform in size throughout the area, but to see 



