On the Palceozoic Bivalved Entomostraca. 413 



XLVI. — Notes on the Palceozoic Bivalved Entomostraca. No. X. 

 Entomis and Entomidella. By Prof. T. Rupert Jones, 

 F.R.S., F.Gi^. 



These two genera of Palaeozoic Bivalved Entomostraca are 

 little known, though comprising several wide-spread species, 

 found in Silurian, Devonian, and Carboniferous strata. To 

 draw attention to these small but well-marked and abundant 

 fossils, by oifering a synopsis of their species, will be useful, it 

 is hoped, to palteontologists. 



I. Entomis, Jones, 1861. 



Cypitdhia, De Koninck, 1841. Mem. Acad. R. Sc. Belg. vol. xiv. p. 18; 



1844. Descr. Auim. foss. Terr. Carb. Belg-. p. 587. 

 Cyjyridina, G. Sandberger, 1842. Leonh. u. Bronn's Jahrb. f. 1842, 



'p. 226; 1845. Jahrb. Ver. Nat. Nassau, Heft ii. p. li'l ; G. & F. 



Sandberger, Verst. Rliein. Sch. Nassau, p. 4. 

 Cypridina, F. A. Romer, 1854. Palseontograpbica, vol. iii. ; Beitr. 



Harzgeb. pp. 19, 28,'42. 

 Cypridma, Riehter, 1856. Denksch. math.-nat. CI. k. Akad. Wien, 



vol. xi. ; Beitr. Palaont. Thiir. Waldes, p. 35. 

 Entomis, Jones, 1861. Mem. Geol. Surv. Gt. Brit, Geol. Edinburgh 



(Map 32), p. 137. 

 Ento7nis, Jones & Kirkby, 1863. Geologist, vi. p. 460; 1864. Rep. 



Brit. Assoc. Newcastle, 1863, Trans. Sect. p. 80; Neues Jahrb. f. 



1864, p. 54; Canad. Nat. Geol. n. s. vol. i. p. 237. 

 Entomis, Bigsby, 1868. Thesaurus Siluricus, p. 74. 

 Eiitotnis, Jones, 1869. Palajoz. Biv. Entom. (Geol. Assoc. ), pp. 2 & 5 ; 



1870. Month. Microsc. Jouru. vol. iv. pp. 185, 187. 

 Entomis, Barrande, 1872. Crust. Poiss. Sil. Boheme (Extrait &c.), p. 41 ; 



Syst. Sil. Boheme, vol. i., Suppl. p. 513. 



Entomis is a bivalved Entomostracon of uncertain alliance. 

 It has an ovato-oblong, bean-like carapace. The valves are 

 strongly indented by a transverse furrow, which begins on the 

 dorsal margin, at about one third of its length from the anterior 

 extremity, and reaches halfway or more across the valve. 

 This is the usual place of the dorsal or nuchal sulcus in several 

 Palteozoic Ostracoda, as : — Aristozoe, Barrande; Orozoe, Barr. ; 

 Cypriddla^ De Koninck ; Cyj^rella^ De Kon. ; Primitia^ Jones 

 & Holl ; Isochilina, Jones ; Lei^erdltia^ Rouault ; Beyrichia, 

 M'Coy ; and Hippaj Barr. 



The surface of each valve sometimes presents in front of the 

 sulcus a rounded tubercle : but this is variable in position and 

 shape ; sometimes it is a spine, sometimes it is wanting. 



The anterior margin is not indented by any sinus or notch, 

 and is therefore without beak or hood. 



In Entomis tuherosa a radiate muscle-spot, in connexion 

 with the tubercle, is shown on casts in Silurian mudstonc from 



