ARISTOZOE (BACTROPUS). 43 



1. Bactropus decoratus, Whidbome (part of Aristozoe). PI. IV, fig. 21. 



1889. Bacteopus decoratus, Whidbome. Geol. Mag., dec. iii, vol. vi, p, 29. 



Description. — The last segment of an abdomen. Subcylindrical, straight on 

 one side and curved on the other, slightly conical downwards, gently swelling at 

 about one-fifth the way down, and tapering rather more rapidly for the last 

 third ; rather oval in section. Surface traversed by about sixty delicate, trans- 

 verse, parallel grooves, of which about ten are deeper than the rest, leaving fine 

 ridges or strise between them ; and indented at the lower end by two oblique and 

 much deeper grooves. 



Size. — Length 12 mm., diameter at the upper end 3 mm., and at the lower 

 end 2 mm. 



Locality. — Lummaton or Barton. A single specimen in the Torquay Museum. 



'Remarks. — This small fossil seems closely allied to those figured by Barrande 

 in the Supplement to vol. i of his ' Systeme Silurien de Boheme,' and described by 

 him under the names of B. longipes 1 and B. tenuis* but it differs from them 

 very greatly in size, and in the much coarser and more regular ornamentation with 

 which it is covered. Both extremities of the specimen are obscure, being partly 

 hidden by the matrix. 



Some time ago Mr. Marr suggested to me the possibility of Bactropus 

 occurring in the Middle-Devonian rocks of England, and showed me a specimen 

 which he had himself collected in Bohemia, and had presented to the Wood- 

 ward ian Museum. I was at once struck with its resemblance to the present 

 fossil, which I had long known ; and my identification was soon afterwards 

 confirmed by Professor Rupert Jones, upon my showing it to him. The chief 

 reason for hesitation was that the English specimen was distinctly furrowed, 

 whereas Mr. Marr's much larger Bohemian specimen, as well as those figured by 

 Barrande, appeared to be smooth. Shortly afterwards, however, Prof. Rupert 

 Jones drew my attention to a paper by Herr 0. Novak, 3 in which he proves that 

 Barrande's Aristozoe, Bactropus, and Geratiocaris debilis* are respectively a 

 cephalo-thoracic valve, a segment of the abdomen, and a telson of the same species 

 of animal ; and that therefore Aristozoe (which is the name he retains) belongs not 

 to the Ostracods but to the Phyllocarida. In this paper, as the Professor 



1 1872, Barr., ' Syst. Sil. Bohein.,' vol. i, Suppl., p. 581, pi. xxi, figs. 1—22, Et. F. 



2 Ibid., p. 582, pi. xxi, figs. 23—31, Et. F. 



3 1885, ' Sitzungsb. kaiser. Bohm. Gesell. Wiss.,' p. 239, pi. i ; ' Remarques sur le Genre Aristozoe, 

 Barrande.' 



* 1872, Barr., ' Syst. Sil.Bohem.,' vol. i, ' Suppl.,' p. 448, pi. xviii, figs. 20—25 ; pi. xix, figs. 20—27, 

 pi. xxvi, fig. 18, and pi. xxxi, figs. 16 — 19. 



