APTYCHOPSIS CORDIFORMIS. 103 



pp. 476 — 478. The specimen there referred to (p. 477) is regarded by the 

 author as showing the lateral aspect of a folded carapace of Spathiocaris Emersoni, 

 Clarke, figured on the same plate (figs. 1 and 2). Though there appears at first 

 sight to be a difficulty in reconciling these figures,^ we are assured by Mr. J. M. 

 Clarke (in letter dated July 11th, 1892, in answer to enquiry on the subject) that 

 the fig. 3 referred to above is not nearly so satisfactory as fig. 12 among his later 

 illustrations, described in detail in the 'Nat. Hist. New York, Palaeontology,' 

 vol. vii, 1888, p. 199, pi. 35, figs. 12—18, where both the open and the folded 

 carapaces are fully treated of. Here also the author has defined and illustrated 

 the gradational forms in successional stages of growth in Spathiocaris Emersoni, 

 from the most minute, only 2 mm. long, to one of 28 mm., and he has a fragment 

 of one that was upwards of 80 mm. in length. 



8. Aptychopsis coEDiFOEMis, sp. nov. Plate XV, fig. 2. 



This obovate carapace (now wanting the front plate) is proportionately 

 shorter and broader than A. prima, and intermediate to that species and its var. 

 secunda in shape. It has a narrower notch than either. PI. XV, fig. 2, shows a 

 pair of valves, one of them imperfect. Measurements : | , 15 mm. ; — , 9 mm.; 

 A, 7 mm. at 60°; ^_,, 7 mm.; I, 6 mm.; V 60°. Two valves, rather broadly 

 sagittate ; carapace acute-obovate. Concentrics broad. In dark-grey, solid, much 

 crushed, finely micaceous mudstone. The proportion of width to length is as 

 eighteen to twenty-one. This, though obovate, is more acute posteriorly and is 

 narrower and sharper behind than any of Barrande's figured specimens. 



From Lower Wenlock beds, Rebecca Hill, Ulverston. Coll. Marr. Cambridge 

 Museum. See ' Catal. Type Fossils Woodwardian Museum,' 1891, pp. 133 and 

 136, and ' Report Brit. Assoc' for 1884, p. 93. This has been labelled " Peltocaris 

 anatina, Salter," and was referred to under that name in the ' Catal. Cambridge 

 Fossils, &c.,' 1873, p. 93 ; but the frontal notch is angular. The median sutural 

 line is raised along the depressed shield, and broad concentric strise are present. 



P. anatina is probably a difi'erent specimen in the Cambridge Museum. 



1 See our Second Eeport in ' Eep. Brit. Assoc' for 1884! (1885), p. 81. 



