Dr. J. E. Gray on a new species of Sphserium. 465 EXPLANATION OF PLATES XIIL XIV. & XV. [The numbers attached to the details of figures i. iii. and v. indicate the same parts throughout.] Plate XIII. Fig. I. Diastylis Rathkii. 2. Carapace seen from above ; showing the manner in which the lateral angles, a, a, meet, without uniting, in front of the an-tennal segments, b. 3. Carapace seen from beneath, with the gnathopoda in position. 4. a. Upper antenna, attached to the carapace, seen from below. 5. Lower antenna; a. olfactory organ. 6. Mandible. 7 & 8. Maxillffi. 10. Maxilliped; a. branchial sac. 11 & 12. 1st and 2nd gnathopoda (2nd and 3rd maxillipeds). 13 & 14. Two anterior pairs of thoracic legs. 15, 16 & 17. The three posterior pairs; a. hairs. 18. Appendages of the two anterior pairs of abdominal segments in the male. 19. Caudal segments and appendages. 20. Section of shell. 21. Gizzard-like structure of stomach. Plate XIV. Fig. II. Cuma scorpioides. Fig. III. Eudora truncatula. Fig. IV. Cuma Edwardsii. Fig. V. Halia trispinosa. Plate XV. Fig. V. Halia trispinosa continued. Fig. VI. Bodotria arenosa (after Goodsir). Fig. VII. Venilia gracilis. Fig. VIII. Larva of Hippolyte varians. 1. Eyes. 2. Upper antenna. 3. Lower antenna. 4. Pair of larval feet (the first maxilliped of adult). 5. One of the two next pair. XLII. — Desct'iption of a new species of Sphserium found near London. By Dr. J. E. Gray, F.R.S., P.B.S. &c. These shells were first brought to me at the British Museum by an intelligent collector, Mr. John Rowse of Brownlow Street, Endell Street. He discovered them on the 17th of May, in the Grand Junction Canal near Kensal Green, and the following day most kindly furnished me with several living specimens for examination. They are not abundant in the locality named. They are decidedly distinct from any of our British specimens, but bear a very great resemblance to Cyclas rhomhoidea of Say, found in the rivers of North America. Ann. ^ Mag. N. Hist, Ser. 2. Vol xvii. 30
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