CERATIOCARIS HALLIANA. 27 



fig. 6 b). Telson and stylets delicately ridged; the former pitted, and its head 

 obscurely wrinkled (PL II, fig. 4). 



The shape of the carapace approximates to that of Dr. James Hall's species C. 

 acuminata and F. Schmidt's G. Noetlingi (' Third Report, Brit. Assoc.,' p. 355). 

 There are marked differences, however, and we have designated this form G. 

 Halliana, in honour of our old and valued friend, who began working at these 

 Phyllocarida as early as 1852. 



A perfect specimen of G. acuminata, Hall, has been described and figured by 

 Dr. Julius Pohlman in the ' Bulletin of the Buffalo Society of Natural Sciences,' 

 vol. v, No. 1, 1886, pp. 28, 29, pi. 3, fig. 2. Its caudal appendages are much 

 like those of G. papilio and G. stygia, the style being relatively short, and the 

 stylets broad and blade-like. The appendages in M. P. G. x y, x ^, and Ludlow 

 Mus. A, are different from these, being thinner, tapering slowly, and pitted in at 

 least one row, as seen exposed. 



The specimens under notice are probably the same as those which Mr. Salter 

 apportioned to G. leptodactylus — " Cephalothorax long, triangular, acute in front, 

 broad and rounded behind. Free abdominal segments 7 to 8 in number, subquad- 

 rate, deeply impressed at the sides. Caudal appendages long, striate ; the central 

 spine (telson) scarcely thicker than the long lateral spines. Surface of carapace 

 smooth, or marked with only very short sparse lines. Abdominal segments 

 strongly striate. The whole animal elongate and more than a foot long." 

 (' Annals Mag. Nat. Hist.,' ser. 3, vol. v, 1860, p. 157.) One particular specimen 

 in the Mus. Pract. Geol. is referred to by Mr. Salter at p. 158 (perhaps PI. II, fig # 

 2 or fig. 4). We are at a loss in fitting the indicated slender appendages of G. 

 leptodactylus to the carapace above described. We have examined the above-men- 

 tioned and other good specimens, labelled G. leptodactylus by Mr. Salter, or at his 

 direction, in which the carapace agrees with his description. One carapace is of 

 large size, nearly perfect, about 125 mm. (5 inches) long, by 55 mm. at greatest height; 

 M. P. G. x|, PL II, fig. 1. A specimen nearly perfect, M. P. G. x y , 60 mm. long 

 by 28 mm., gives no certain indication of the length of its telson and its two 

 stylets, for they are crushed off short (PL II, fig. 2). The abdomen exposed is> 

 about 50 mm. in length. 



There is also a well-preserved small specimen, M. P. G. x ^, with its carapace' 

 measuring only 25 mm. in length and 11 mm. in height, from the Lower Ludlow of 

 Bow Bridge, Ludlow (PL II, fig. 4). This is labelled " G. leptodactylus," but 

 belongs to the same species as the foregoing. Its caudal appendages are perfect, 

 with the telson (25 mm.) about one third of the length of the whole animal; and 

 they differ from M'Coy's G. leptodactylus in their proportions. 



PL II, fig. 4 and PL Y, fig. 6 may possibly belong to G. tyrannus, for their 

 caudal appendages agree with some referred to that species (see p. 22). For con- 



