GEOLOGICAL SURVEY IN SILURIAN ROCKS OF SOUTH OF SCOTLAND. 



845 



The remains of Drepanaspis Gmiindenensis occur in a pyritised condition in the 

 dark purple roofing-slate (Hunsrtickschiefer) of Gmiinden, a mode of preservation which, 

 though yielding beautiful fossils to laborious and careful preparation, forbids their 

 affording any results to microscopic examination. It was a fish of considerable size, and 

 large examples must have attained a length of over two feet. 



From the accompanying sketch it will be seen that, as in Thelodus, the fish is 

 divided into two parts — an anterior, broad and depressed, corresponding to the head 

 and body, and a posterior, or tail, terminating in a heterocercal caudal fin. The anterior 



'ig. 5.— Drepanaspis Gmiindenensis, Schluter ; restored outline of the dorsal aspect, the surface ornament omitted, and the 

 tail twisted round so as to show the caudal fin in profile ; c. , central plate ; p. I., postero-lateral plates ; r. , rostral plates ; 

 x. , orbits 1 



>art forms a broad oblong carapace, rounded in front, abruptly truncated behind, where 



here is on each side a prominent though rounded angle. From the middle third of the 



ransverse posterior margin the tail arises. The carapace consists of numerous bony 



lates, large and small. In the centre there is a large median dorsal plate (c) of a 



miewhat ovate-hexagonal contour, the anterior margin being short and somewhat 



raight; the posterior is more rounded, and is also acutely notched in the middle. 



he two postero-lateral angles are formed each by a large, narrow, triangular falciform 



ate (pi), which narrows to a very acute point more than half-way to the front of the 



rapace. The rest of the space is covered by a multitude of small polygonal plates, 



ostly hexagonal in contour, but the anterior margin itself is generally formed by a 



