552 E. W. Shuler — New Ordovician JEurypterid. 



The posterior margin of the proximal joint is supplied with 

 two prominent spines or flattened bristles, the larger of which 

 occupies the distal corner. This is the largest spine preserved. 

 It has a length of 4l mm . The width, 2 mm , is fairly uniform 

 along its whole length. In common with the other spines it 

 originates in a projecting alveolar process or ring-like swelling 

 of the integument at the base, which from its unusual develop- 

 ment, is a significant characteristic of this species. The smaller 



Figs. 1-6. 



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m 



;3 1 

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n 



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Figs. 1-6. Stylonurus (Ctenopterus) alveolatus sp. n. 



Figure 1. A part of the telson spine with the impression of two abdomi- 

 nal segments. Figure 2. Moulds of the tubercles on a fragment of the cara- 

 pace ( x 2). Figure 3. Endognathite probably belonging to the first pair of 

 post-oral appendages. Figure 4. Endognathite belonging to the second or 

 third pair of post- oral appendages. Figure 5. Undetermined fragment of 

 an appendage. Figure 6. A fragment of a joint from the walking leg. All 

 figures except figure 2 natural size. The specimen represented in figure 4 is 

 to be considered the holotype of the species. 



spine has a measured length of 14r mm . The broken jagged ends 

 indicate that the spines were originally much longer. 



The adjacent segment shows four alveolar processes with 

 parts of three spines preserved. Again the distal corner was 

 occupied by the largest spine. All spines have been lost from 

 the third segment but five alveolar processes are seen, the dis- 



