Fig. 13

Echinometra lucunter (Linné), USNM E45614, SE micrographs of broken sections through primary spines. a Stub D1, broken end of spine. b Stub D2, oblique view of small spine. c Stub D1 (different specimen from a, d, e), broken end of spine. d Stub D1 (different specimen from a, c, e), broken end of spine. e Stub D1 (different specimen from a, c, d), broken end of spine. f Stub D2 (different specimen from b), broken end of spine. All scale bars represent 500 μm