Turonian-Santonian echinoids from Egypt Author Mohamed Abdelhamid, Marouf Abdel-Aty Author Moustafa Azab, Mahmoud text Geodiversitas 2012 2012-09-30 34 3 575 615 http://dx.doi.org/10.5252/g2012n3a7 journal article 10.5252/g2012n3a7 1638-9395 5378120 28D04AB5-0407-40DF-ABB0-0C1184A27655 Rachiosoma irregulare Fourtau, 1921 ( Figs 7G ; 8E, F ) Rachiosoma irregulare Fourtau, 1921: 39 , pl. 5, figs3, 4. — Abdelhamid & El Qot 2001: 18 , fig. 5D, E. — El Qot 2006: 137 , pl. 31, figs 8, 10a, b. MATERIAL EXAMINED. — Three specimens from the Turonian of Wadi Abu Qaada (Wata Formation), AS- UAQE 5-7, Wadi Abu Qaada echinoid horizon 4 ( QEH 4). DESCRIPTION Test diameter attaining 15.5-24.6 mm . Adapical surface convex, high (H/D = 0.47-0.54). Outline of apical disc pentagonal, caducous ( Fig. 8E ) (La/D = 0.43-0.47). Ambulacral area wide (Wa/Wi = 0.62- 0.75). Poriferous zones uniserial. Major ambulacral plates quadrigeminate, but they are trigeminate in three plates adjacent to peristome. Two columns of granules occur around the perradial suture. Interambulacral area with two columns of imperforate,crenulated, and nonconfluent primary tubercles. Adradial extrascrobicular surface wide and occupied by very small tubercles ( Fig.7G ). Interradial extrascrobicular surface occupied by two columns of smaller granules. REMARKS This species is distinguished from R . rectilineatum (Péron& Gauthier, 1881) in having wider ambulacra at the apex, well developed ambulacral tubercles on adapical surface, relatively higher test (H/D = 0.47-0.54 against 0.38-0.49 in R . rectilineatum ), and the mamelonated granules on the adradial extrascrobicular surface reach both the apical disc and peristome whereas in R . rectilineatum they are more developed but confined to the ambital area.