306 Faunoj of the Lower Devonian Beds of Torquay. 



The thorax is not well exhibited, being crushed and hidden by 

 matrix, but the last three or four segments are sufficiently perfect 

 to show the tubercles on the axis and the nodes on the pleurae. The 

 pygidium is nearly complete, though distorted ; the right lateral 

 lobe is almost uninjured ; the axis exhibits its characters w^ell in 

 the cast and impression, and the bifurcated terminal spine shows 

 distinctly on the left side of the imjDression, but the cast has the 

 posterior end of the pygidium broken off. 



There is also a portion of a large pygidium from the same locality 

 in the Sedgwick Museum (S. 6), which is represented by the internal 

 cast and the external impression, and may belong to the same species. 

 This specimen has its axis, measuring over 30 mm. in width, at its 

 front end, but only four rings are preserved. Of these the first and 

 third rings bear two pairs of tubercles, of which the outer ones are 

 the larger ; the second ring only possesses one pair corresponding 

 to the outer ones, and the fourth ring only the inner pair. 



With regard to the relations of this species, we must first notice 

 the close resemblance of the pygidium to that of H. elongatus, 

 Salter,^ from the Lower Devonian of Meadfoot, but the forked mucro 

 at its extremit}^ is peculiar, and recalls the species from the Rhine 

 described by Koch^ as H. aculeatus, though in his figure this special 

 feature is not represented. It may be remarked that a similar 

 peculiar bifurcated termination of the pygidium is present in some 

 American species of Dalmanites (Odontocephalus) from the Devonian 

 (e.g. D. selenurus Eaton'' and D. bifidus Hall^). The head-shield 

 and thorax of H. Cham-pernoivnei Woodw.® appear to possess nearly 

 the same characters as our new species, particularly in the 

 tuberculation of the head-shield, but the anterior margin, prora, 

 and course of the transverse suture are not known in the imperfectly 

 preserved type-specimen which was figured by Woodward, and the 

 pygidium appears to be different in its axial characters, and certainly 

 lacks the j)osterior forked termination. The axial rings of the thorax 

 are also stated to bear only one pair of tubercles instead of two pairs. 

 The head-shields of H. armatus Burm.*' and H. stibarmatus Koch,''' 

 so far as they are known, seem allied to H. hifurc.atus, especially 

 in their tuberculation, but the ptygidia are different. 



1 Salter, Mon. Brit. Trilob., p. 122, pi. x, figs. 1-2. 



^ Koch, op. cit., p. 93, t. i, fig. 7. 



3 Hall, Palffiont. New York, vol. vii, 1888, p. 49, pi. xis, figs. 15-2L 



* Ibid., p. 53, pi. xiB figs. 22-5. 



= Woodward, Geol. Mag;, 1881, p. 489, PI. XIII. 



^ Koch, op. cit., p. 84, t. i, figs. 1-4, and p. 151. 



^ Freeh, Leth. Palajoz., Bd. ii, 1897-1902, p. 218, text-figure. 



{To be continued.) 



