178 DR. T. DAVIDSON ON EECENT BRACK lOPODA. 



Pigs Rock, South Australia. 28. Interior of ventral valve. 29. Interior of dorsal valve, show- 

 ing the loop. .30,31. Interior of Ijoth valves, nuich enlarged. 32. Loop of a young specimen. 

 Figs. 33, 33 a. Mar/asella fibula, Reeve, sp. From the type in the Zool. Dept. of the British Museum ; 

 said to have been dredged in Bass Strait, South Australia; probably a large example of 

 Magasella Cumingl. 



Plate XVIII. 



Fig. 1. Magasella (?) radiata, Dall. Popoff's Strait, north-west of Alaska. Ball's type, in the 

 National Collection, Washington, D.C. This enlarged drawiug was sent to me by Mr. Dall. 



Figs. 2-3 a. Magasella (?) incerta, Davidson. 2. Exterior of the shell. 3, 3 a. Interior of dorsal valve, 

 enlarged. Dredged by the 'Challenger' Exjjedition west of St. Thomas, Danish West Indies. 

 In the Zool. Dept., Bi-itish Museum. 



Fig. 4. Magasella (f) l(evrs,T)a\\. From Orange Harbour, Patagonia. Smithsonian Museum, Washington, 

 D.C. 



Figs. 5, 5 a. Magasella (?) Malvinm, d'Orhiguy. After figs, in Voyage Amer. Mer. vol. v. pi. 85. 

 figs. 27-29. Malvines. 



Figs. 6-9. Larjueus raliforniciis, Koch, sp. 6. A very large example (Davidson Collection, Geol. Dept., 

 British Museum) . 7. A specimen in the National Collection, Washington, D.C. 8, 8«. In- 

 terior of dorsal valve, showing the loop. 9. Kiister's fig. of his T. Kochii, Chemn. Couch. -Cab. 

 vol. vii. tal). 2 «. fig. 9. All from off the Calif ornian coast. 



Figs. 10-13 6. Laqiieus califormcus, var. vancouvericHsis. A series of specimens of different forms and 

 ages. Oft' Vancouver Island. 12. Interior of dorsal valve. (Davidson Collection, Geol. Dept., 

 British Museum). 



Figs. 14-18. Laqueus pictus, Chemnitz, sp. A seiies of specimens of different ages from Japanese waters. 

 14, 15, 17, 18. (Davidson Collection, Geol. Dept., British Museum.) 18. Interior of dorsal 

 valve, showing the loop. 10. Specimen figured by L. lleeve (Mus. de Burgh). 



Plate XIX. 



Figs. 1-5. Laqveus rubellus, Sowerby, sp. From Japanese waters. 1, 2, and 5. Large examples 

 (Davidson Collection, Geol. Dept., British Museum). 3-3 6. In Zool. Dept. of the British 

 Museum. 4, 4 a. Sowcrby's figured type. 



Figs. 6-7 6. Laqueus siiffustis, Dall. From the Wharf at Yokohama, Japan. 6. Type in Smithsonian 

 Cabinet, Washington, D.C. 7-7 b. Davidson Collection, Geol. Dept., British Museum. This 

 is the shell which was erroneously referred by Adams to T. cranium. 



Figs. 8-10 a. Megerlia Jeffreysi, Dall, = young of Laqueus californicus. From Port Etches, Alaska 

 Territory. Types in the National Museum, Washington, D.C. 10,10 a. Interior of the dorsal 

 valve, much enlarged. 



Figs. 11-20. Megerlia truncata, hinne, sp. 11-14. Diflcrent forms and ages. 11-116. OiJ Teneriff"e, 

 dredged by the ' Challenger' Expedition. 12, 13, 14. Mediterranean forms, all in the Davidson 

 Collection, Geol. Dept., British Museum. 15, IG. Interior of the dorsal valve of Megerlia 

 truncata, showing loop. 17. Interior of the same valve to show the labial appendages. 

 18. Interior of the ventral valve of Megerlia truncata, after E. Deslougchamps, showing the 

 entire mantle ; vc, visceral cavity ; ap., calcified portion of the mantle forming the antei-ior 

 wall of the visceral cavity ; sv., calcified portion of the mantle on the course or direction 

 of the large sinus ; R, branch and smaller branches or subdivisions of the sinus on which the 

 brachial apparatus does not extend, enlarged four diameters. 

 Fig. 19. Interior of the dorsal valve of Megerlia truncata, also after Deslougchamps, showing the 

 complete mantle (the right branch of the brachial apparatus or loop has been removed in 

 order to show better the bearing of the diflerent portions of the pallial apparatus) ; cv., visceral 



