194 BRITISH PALEOZOIC PHYLLOCARIDA. 



Roemer's figures (reproduced PI. XXIX, figs. 15a — c) of this obscure fossil may 

 possibly be referable either to a portion of a bivalved carapace, with a median 

 dorsal ridge (or hinge-line), or to a single convex valve, with a lateral longi- 

 tudinal ridge such as that of Ptychocaris ; in either case filled with matrix, and 

 broken across. Being convex and ridged on one face, and nearly flat on the 

 other, it shows a flattened subelliptical (Roemer's) or suboval (Kayser's) section. 

 It has an ornament of straight and inosculating striae, connected by oblique strias, 

 sinuous and traversing the interspaces. This is analogous to the irregular inter- 

 linear meshwork in PI. XVIII, fig. 8, and PI. XXI, fig. 11. 



Dr. Kayser's figures give this little fossil straighter sides, with the ridge 

 oblique, and the section more of a flattened oval shape. The surface bears longi- 

 tudinal stria?, parallel to the sides, and on one side to the ridge, but slightly 

 oblique to it on the other. 



From the Hercynian Limestone (latest Silurian or earliest Devonian) in the 

 Klosterholz, near Ilsenberg, Hartz. 



The late Ottomar Xovak, in 1888 informed us that this fossil, as figured by 

 Kayser, shows some resemblance to his Ptychocaris, 1 which occurs in the equiva- 

 lent horizon, namely, the " Hercynian " of Beyrich and Kayser = " Etages F, G, 

 and H" of Barrande. 



The Gastric Teeth of Dithyrocaris. 



In the ' Geological Magazine,' vol. ii (1865), a paper by one of us " On some 

 Crustacean Teeth from the Carboniferous and Upper Ludlow Rocks of Scotland " 

 describes and illustrates some of these curious little fossils. At page 401 it is 

 stated that il So long ago as 1843 the late General Portlock (at that time a 

 captain of the Royal Engineers conducting the Geological Branch of the 

 Ordnance Survey of Ireland), in his ' Report on the Geology of the County of 

 Londonderry,' figured the teeth of Dlthyrocaris in pi. xii, fig. G, of that work ; 

 and at page 315 he observes, " Fig. 6 represents bodies which are frequently 

 found on the specimens of this crustacean, and in this instance together, as 

 represented in the figured specimen, they each exhibit a single row of tubercles, 

 and were in all probability connected with the masticatory apparatus, which it is 

 probable, therefore, was highly developed in this large species." The figure here 

 referred to was reproduced in the ' Geol. Mag.,' pi. xi, fig. 8 ; but is now much 

 more accurately drawn (from the original specimen) in PI. XXVI, fig. 44. We 



' 'SitzungBb. bohm. Ges. \Vi>s.,' 1SS5, pp. 3-13— 316, and plate. This Phyllocarid is related to 

 lioth Ceratiocaris and Dithyrocaris. 



