498 F, R. Cowper Reed — Fossils from Haverf or divest. 



Remarks. — The true generic position of this little shell (of which 

 I have seen only one well-preserved specimen) is somewhat difficult 

 to decide. At first I was inclined to put it in Goniophora, though 

 that genus is typically Silurian. But on comparison with the 

 description and figures of the American genus Whitella ' from the 

 Ordovician of Ohio, Minnesota, etc., the shape, the presence of 

 the strong umbonal ridge and escutcheon lead me to associate it 

 preferably with the latter genus. Wh. sterlingensis, Meek & Worthen,^ 

 and Wh. prcecipta, Ulr.,^ are species which may be compared with it, 



AmbONYOHIA (BySSONTOHIA) cf. RADIATA, Hall. 



There is one fragmentary cast of a large Lamellibranch from the 

 Slade Beds in Mr. Turnbull's collection which may be compared 

 with Hall's Ambonychia radiatn * from the Hudson River group. 

 The umbonal portions of both valves in juxtaposition are preserved 

 as internal casts, and there is also the imprint of the exterior of one 

 valve. The ventricose shape of the valves, the pointed incurved 

 beaks, and the regular, low, radiating plications, 30-40 in number, 

 ornamenting the surface, can be distinctlj^ seen, but no other 

 structural featui-es are distinguishable. The fragment which repre- 

 sents the anterior portion of the shell measures about 27 mm. in 

 length, but the shell when complete must have been about twice 

 this length. The occurrence of this specimen is worth noting, as 

 no example of a Lamellibranch resembling A. radiata has been 

 previously recorded from the Slade Beds ; but it is to be hoped that 

 better material for description will be subsequently obtained. The 

 species has been found in the Corona Beds of Cross Fell. It may 

 be mentioned that Uh'ich ^ has put A. radiata into a new genus 

 Byssonychia, separating it from the typical Ambonychia belli' 

 striata. Hall. 



MoDiOLOPSis Martini, sp. nov. (PI. XXIV, Figs. 1-4.) 



Description. — Shell small, obliquely elongate, expanding 

 posteriorly, convex. Cardinal margin straight ; anterior end small, 

 narrowed, rounded ; beaks small, obtuse, incurved, moderately 

 prominent, situated at about one-fifth or one-sixth the length of the 

 shell from anterior end ; inferior margin gently sinuated at about 

 one-third or one-fourth of its length, curving round gently at 

 posterior extremity; posterior end of shell broad, nearly twice as 

 wide as anterior end, strongly rounded. Valves convex, more or 

 less ventricose, with indefinite rounded, broad, umbonal ridge 

 running obliquely back from beak ; shallow indistinct sulcus 

 running from beak in front of umbonal ridge to inferior margin, 

 which it slightly sinuates ; surface of valves behind umbonal ridge 

 more or less flattened. Surface of shell ornamented with fine 

 concentric growth-lines and stri^, some of which are stronger 

 than others. 



1 Ulrich : op. cit., p. 564. 



* Ulrich: op. cit., p. 567, pi. xli, figs. 27, 28. 

 5 Ulrich: op. cit., p. 574, pi. xli, figs. 15, 16. 



* Hall: Pakcont. New York, vol. i (1847), p. 292, pi. Ixxx, figs. ia-l. 

 5 Ulrich: op. cit., p. 498. 



