60 



M. RUTA 



B 



Fig. 4 Jidiaecarpus milnemrum gen. et sp. nov. Late Ordovician, Upper Ashgill. Rawtheyan. Upper Ktaoua Formation. Morocco. Camera lucida sketches 

 of outline of supracentralia in different individuals. A, EE 3072, x 6. B, EE3144, x 7. C, EE 3119, x 7. 



subequal size (Fig. 4; PI. 1, figs 2-5; PI. 2, figs 2, 4-5; PI. 3, figs 2, 4; 

 PI. 5, figs 1-2; PI. 7, fig. 2, 4-5; PI. 8, fig. 3). 



A large suranal plate (Figs 1-2, 5; PL 1, fig. 5; PI. 2, figs 4-5,4; PI. 

 3, fig. 4; PI. 4, fig. 5; PL 5, figs 1-2; PL 7, figs 2, 4; PL 8, fig. 3), 

 sloping slightly ventralward towards its posterior margin, is present 

 between the rearmost margins of M'^ and M^. Its posterior margin 

 roofs over the anal opening. In some specimens, the suranal is 

 broadly trapezoidal in outline. In others, it is rectangular or, rarely, 

 roughly elliptical. Although the suranal is variable in shape, it is 

 always possible to distinguish four margins: a straight to gently 

 sinuous anterior margin loosely articulated with a variable number 

 of posterior supracentralia; two irregularly sinuous lateral margins in 

 contact along their posterior half with the medial margins of M', and 

 M^ and along their anterior half with the rearmost part of the medial 

 margins of M'^ and M^; and a broadly convex, posterior margin with 

 a variable degree of curvature and usually displaying a well devel- 

 oped fringe (see description of stereom below). The posterior margin 

 is usually very slightly offset with respect to the position of the oro- 

 anal axis. The dorsal surface of the suranal plate is flat to very gently 



convex in its central part and flat along its posterior margin and 

 slopes gently ventralward near its lateral margins. 



Ventral INTEGUMENT. The ventral integument (PL 2. figs 1,3;P1. 

 3, figs 1 , 3, 5; PL 4, figs 1-2, 4) is flat and divided by the zygal bar into 

 two antero-posteriorly elongate areas of slightly different size, the 

 left area being slightly broader than the right area. The infracentralia 

 are generally more poorly preserved than the supracentralia, but 

 seem to have been more irregular in outline and of various shapes and 

 sizes. As in the case of the supracentralia, they do not seem to have 

 been imbricated or to have shown a regular arrangement, but their 

 boundaries are difficult to delimit. 



Unfortunately, in none of the specimens of Juliaecarpus is the 

 ventral integument complete and its posterior part is invariably 

 damaged or missing. Therefore, the reconstruction of the 

 infracentralia which floor the anal opening is only tentative and it is 

 impossible to say whether the ventral margin of the anus was 

 bordered by flexibly articulated, narrow, elongate platelets arranged 

 in a fan-like pattern (as in the case of the ankyroid Amygdalotheca 



PLATE 4 



Juliaecarpus milnemrum gen. et sp. nov. Late Ordovician, Upper Ashgill, Rawtheyan, Upper Ktaoua Formation, Morocco. All latex casts coated with 

 ammonium chloride. 1, EE 3069, x 10; heavily disrupted theca in ventral aspect; note shape and proportions of posterior zygal process. 2, EE 3115. x 10; 

 incomplete and laterally compressed theca in ventral aspect. 3, EE 3181, x 15; isolated marginal element in internal view, possibly M,. 4, EE 3162, x 10; 

 incomplete and disrupted theca in ventral aspect. 5, EE 3162, x 10; posteriorly disrupted theca in dorsal aspect with partially preserved supracentralia. 



