BRITISH FOSSILS, 



3 



TERTIARY (EOCENE) SPECIES OP ASTROPECTEN. 



[Genus ASTROPECTEN. Linck. (Sub-kingdom Radiata. Class Echinodermata. 

 Order Asteriadse. Family Asterise). Body stellate, few (five) rayed ; no vent ; rays flat 

 on both sides, regular ; surface of body, and upper sides of arms covered with paxillse. 

 Ambulacra with two rows of suckers, bordered by spines. Margins of the arms bordered 

 by a double row of conspicuous plates. — The genera Stellaria of Nakdo and Asterias 

 (restricted) of Agassiz are synonymous.] 



Fig. 3. 



ASTROPECTEN CRISPATTTS. 



E. Forbes, in " Memoirs of the Geological Survey of Great Britain,'* 

 vol. ii. part 2, p. 479 — (icon.) Ansted, " Geology," vol. ii. p. 66, woodcut. 



Diagnosis. A. radiis late la?iceolatis, attenuatis^ angulis intermediis 

 valde ohtusis ; ossiculis marginalibus anguste oblongis^ numerosis, spiniferis ; 

 disco lato. 



Description. — Disk broad, rays lanceolate, broad at their bases, 

 attenuated at their extremities, and forming very obtuse angles at their 

 junctions with each other ; the lanceolate portion of the arms is about 

 one-fifth longer than the disk is broad. They are bordered by closely 

 set oblong, narrow plates, very numerous, about 36 on either side of each 

 ray in the largest specimen examined. These marginal plates decline 

 outwardly. Those bordering the angles of junction preserve their 

 dimensions. All the marginal plates bear at their exterior and superior 

 edges short obtuse lanceolate spines. The inferior marginal plates are 

 curved more regularly than the superior. The ossicula of the surface 

 and framework of the disk are very irregular. The section of a,n arm 

 shows that it was of inconsiderable thickness, and, from the peculiar 

 shape of the marginal plates, edged at the sides. The ossicles bordering 

 the ambulacra are of considerable dimensions. The extremities of the 

 arms seem (judging from the fragment fig. 1, c), to be much attenuated ; 

 but the plates bordering them preserved the proportions of those nearer 

 the body. The breadth of the disk in the largest specimen I have seen 

 is one inch four-twelfths. The rays are nine-twelfths of an inch broad 

 at their bases. The marginal ossicles are four-twelfths of an inch 

 broad, by less than one-twelfth long. The thickness of a ray is less 

 than two-twelfths. 



Locality and Geological Position. — In the London clay of Sheppey, 

 where specimens are not uncommon. Those represented at figs. 3 h and 

 3 c, were communicated to the Geological Survey by Mr. Stokes. 

 Fig. 3 a is a remarkably fine specimen, in the collection of Mr. Bower- 

 bank. 



