ON THE FOSSIL PHYLLOPODA OF THE PALJEOZOIC KOCKS. 95 



Where the front edges are elliptically ronnded, there would he a 

 slight notch in the same position as that in Aptychopsis ; hut there is no 

 evidence of any cephalic or rostral piece having occupied it, On the 

 contrary, the genus may have heen truly- hi valve, like Estheria and other 

 such Phyllopods. This genus is known in the Lower and Upper Silurian. 



I. Pinnocaris Lapworthi, R. Etheridge, Jun. ' Prcc. R. Phvs. Soc. 

 Edinb.' vol. iv. (1878), p. 169, pi. 2, tigs. 3-5; 'Fossils of Girvan,' 

 &c.' p. 280, pi. 14, figs. 17-20. 



Figs. 18, 19, and 20 have the postero-ventral edge of the valve much 

 more contracted than fig. 17 (imperfect) would have if completed accord- 

 ing to the contours of its remaining lines of growth. Possibly a variety 

 is here indicated. Moreover, the front edge of fig. 17 is much more 

 rounded (more semicircular) than the others, admitting of little or no 

 cephalic piece. These are from the Lower Silurian at Balcletchie, 

 Girvan, Ayrshire. A specimen of the form or variety shown by fig. 17- — ■ 

 that is, witli the hinder portion less pinched in — is in the British Museum, 

 from the Upper Silurian of Kendal. 



The shield is triangular-obovate, if the two lateral pieces be laid out 

 together. 



Length Greatest width of different examples 



mm. nun. 



32 12 



30 10 



28 8 



!No Goniatites accompany these specimens. 



Caudal Appendages. 



From the analogy of allied forms, we should expect that these 

 Apudiform Crustaceans had more or less extended abdominal segments 

 and caudal spines. With regard to this part of their organism we have 

 not much to remark, except that a few such styles or stylets as are 

 attached to the telson in known forms have been found in strata containing 

 Discinocaris, Peltocaris, or Aptychopsis. Thus, at the Skelgill Beck, 

 Ambleside, in the Coniston (Upper Silnrian) nmdstones, in which 

 Discinocaris and Peltocaris occur, Mr. J. E. Marr found a small tapering- 

 caudal spine, 15 mm. long, and delicately striate (now in the Cambridge 

 Museum). This may have belonged to one of the forms just mentioned. 

 So, also, there is a small thin spine, 35 mm. long, and apparently dotted 

 with the bases of minute prickles, in the British Museum, from the 

 Riccarton (Upper Silurian) beds of Shankend, near Hawick ; and two 

 (probably the remnant of a set of three), one 35 mm long and fluted, 

 and the other 20 mm. long, from the Buckholm beds (Upper Silurian) of 

 the Gala group, Meigle Hills, Galashiels. These are lai'ge enough for 

 Ceratiocaris, but only Aptychopsis and Peltocaris are known in these 

 strata. 



We may add that a few small caudal spines, 20 mm. long, have been 

 found by Mr. Marr in the Upper Arenig Slates at theNantlle tramway, 

 Pont Seiont, near Caernarvon. Here they are associated with Caryocaris. 

 See ' First Report on the Palasozoic Phyllopoda.' 



