Vol, 54.] THE DECAPOD CRUSTACEA. OF ENGLAND. 41 



separated from the cardiac by a V-shaped sulcus. Posterior margin 

 of the carapace abruptly declivous. Buccal opening as wide as 

 long. Sternal plastron large, broadly ovate. Male abdomen 

 hastate, tapering rapidly to a small telson ; sulci between the third, 

 fourth, and fifth segments indistinct. Chelas rather unequal in 

 size ; meropodite remarkably robust, as large as, or larger than, the 

 propodite. 



Distribution. — London Clay of Sheppey and Portsmouth. Eed 

 ^rag (derivative) of Felixstowe. 



Genus Xanthilites, Bell. 

 Xanthilites Bowerbankii, Bell. 



1858. BeU, Monogr. pt. i, p. 17 & pi. ii, figs. 2-6. 



1859. PseuderipJiia M' Coyi, Eeuss, ' Zur Kenntniss foss. Krabben,' Denkschr. 

 k. Akad. Wissensch. Wien, vol. xvii, p. 54 & pi. xviii, figs. 4-6. 



1859 ? Leiochilus Morrisi, Reuss, ibid. p. 56 & pi. xviii, fig. 7 ; see Portunites 

 incerfa. 



1863-64. Xanthilites BowerhanTcii, Milne-Edwards, Ann, Sci. Nat. ser. 4, vol. xx 

 (1863) pi. xi, figs. 1 & 2 ; ser. 5, vol. i (1864) p. 47. 



Supplementary. — Antero-lateral margin of the carapace slightly 

 arcuate. The postero -lateral margin — described by Bell as very 

 ishort — is longer than the antero-lateral, nearly straight, inclining 

 inward. Dorsal surface bears granules, ten to twelve in a square 

 centimetre, irregularly disposed, most of them having an apical 

 .(setigerous ?) pit. A triangular lobe occurs between the base of 

 the mesogastric and the branchial lobes, representing an unusually 

 distinct hypogastric. Sternal plastron broadly lanceolate, a fifth 

 longer than wide ; episternum trilobate, minutely granulated, half 

 ihe width and a fourth the length of the sternal plastron. 



RemarTcs. — Bell has given a diagram (fig. 6) of the abdomen, 

 which he considered to be that of the female, but I venture to 

 doubt that determination. In all Brachyura, both fossil and recent, 

 so far as I can ascertain, the segments of the female abdomen, pos- 

 terior to the third, are as wide as, or wider than, those preceding it, 

 and thus are rendered adaptive for the normal function of supporting 

 and protecting the ova. In some genera this lateral expansion is 

 :slight, but it is always recognizable. The hastate form appears to 

 be peculiar to the male : as all the specimens of the abdomen of 

 this species which I have examined are of this form, I regard them 

 .as belonging to that sex. 



This species, together with Plagiolophus Wetherellii and Portunites 

 incerta, was concurrently and independently described, but under 

 different names, by Beuss and by Bell. The description is given by 

 Heuss in a valuable communication made in 1857, but not published 

 in full until 1859.^ The volume of the Palaeontographical Society 

 <;ontaining Bell's monograph, dated 1857, was issued in 1858, and 

 became available for reference at an earlier date than the German 

 publication. Under these circumstances I have recognized Bell's 

 43laim to priority, and have continued the names which he employed. 

 Keuss alludes to this coincidence of publication in a copious note 

 fippended to his paper. 



^ Denkschr. k. Akad. Wisseusck. Wien, vol. xvii. 



