50 



ASAPHUS CAUDATXJS.* Briinnich. Brongn, Cast 

 No, 17. 



Clypeo antice subrotundato, postice valde emargi- 

 nato, angulo externo in mucronem productoj oculis 

 exsertis, conicis, truncatis, distincte reliculatisj post 

 abdomine in caudam membranaceam,acutam extenso. 

 (Vide Brongniart.) 



The middle lobe of the buckler is marked by three 

 transverse plicae or folds on its posterior part, and 

 its cheeks or lateral portions are triangular^ the pos- 

 terior exterior angles of which, are acute, and con- 

 siderably elongated. The cheeks are furnished with 

 conical, truncated, semilunar and externally convex 

 tubercles, which were beyond all doubt the eyes of the 

 animal, being reticulated as in those of the Limulus. 

 The middle lobe of the back is narrow, and has twelve 

 articulations. The lateral lobes are composed of 

 double ribbed costal arches. Beyond the lateral lobes 

 and the caudal termination, there is a smooth, thick 

 membranaceous expansion, which forms an acute 

 projection below the central portion of the tail. 



The specimen in the Philadelphia Museum, by 

 which I have identified this species, is marked as 

 coming from Ripley, Ohio. It reposes on a frag- 

 ment of ash coloured limestone which contains also 

 a mutilated specimen of what seems to be a calymene, 

 and a few small terebratulse, Sec. 



* From the Latin word for " tailed," 



