On the PalcBozoic Bivalved Entomostraca. 395 



Setffi in four rows of pairs ; dorsal setse (in posterior region 

 of body) much longer than ventral. Nephridiopores in front 

 of ventral set^. Two pairs of spermathecee in segments seven 

 and eight. 



EXPLANATION OF PLATE XXIII. 



Fig. 1. Phreoryctes Smithii, uat. size. 



Fig. 2. Anterior segments from ventral aspect, magnified, sp, sperma- 



tliecal pores, J openings of vasa deferentia, 5 openings of 



oviducts. 

 Fig, 3. Genital segments, t, testes ; o, ovaries ; v.d, vasa defereutia ; 



o.d, oviducts ; sp, spermathecee ; s, setae ; n, nerve-cord. 

 Fig. 4. Fi-agment of testis, highly magnified. 

 Fig. 5. Fragment of ovary, highly magnified. 

 F'ig. 6. Section through funnel of vas deferens, st, septum ; /, funnel ; 



v.d, vas deferens. 

 Fig. 7. Section through one of posterior segments, s, setse ; n, nerve- 

 cord ; al, intestine ; d.v, dorsal vessel ; v.v, ventral vessel ; 7ip, 



nephridium. 

 Fig. 8. Surface view of the uephridiopore (w^) and setae (s). 

 Fig. 9. Spermatheca, transverse sections, c, near to external orifice ; b, 



near distal end. 

 Fig. 10. Seta. 



LIII. — Notes on the Palceozoic Bivalved Entomostraca. — 

 No. XXV. On some Silurian Ostracoda from Gothland'^. 

 By Prof. T. Rupert Jones, F.R.S., F.G.S. 



[Plates XXI. & XXII. f] 



Prof. Gustav Lindstrom, of the State Museum, Stockholm, 

 having confided to me in 1886 a fine series of Ostracoda from 

 the Silurian rocks of Gothland for examination, I had much 

 pleasure in 1887 in comparing them with such as are known 

 from other countries and in determining what seemed to me to 

 be their generic and specific alliances. Late researches 

 among the British species, especially those collected by 

 Messrs. J. Smith and G. E,. Vine in Shropshire |, enabled me 

 to arrive at conclusions more confidently than I could other- 

 wise have done ; and the results were given by me in the 



* For No. XXIV. see Ann. & Mag. Nat. Hist, for June 1887. 



t These Plates have been drawn with the aid of a grant from the 

 Royal Society for illustrating the fossil Entomostraca. 



X Ann. & Mag. Nat. Hist, for April 1880, May 1886, IVIarch 1887, and 

 June 1887. 



