186/.] MESSRS. BAIRD AND ADAMS ON CHINESE SHELLS. 491 



open umbilicus, and are of a large size ; but along with these are a 

 number of specimens which differ in size and have the umbilicus 

 closed. In almost every respect the smaller of these shells resemble 

 the Nanina redjieldi of Pfeiflfer ; but as there is one specimen with 

 a closed umbilicus, nearly of the same size as the true N. ravida, and 

 agreeing with it in every other point, it appears to be very difficult, 

 with the exception of the closed umbilicus, to separate the two spe- 

 cies from each other. There is also a small species of Helix in the 

 collection, which appears to be an elevated variety of the H. ciliosa 

 of PfeiflPer. 



6th. Among the Vnionidce are several specimens of the rather rare 

 Unio nodosus of Wood, and one valve, exactly similar to the Barbala 

 magnifica of Lea from Japan. Arconaia lanceolata {Triquetra lan- 

 ceolata, Lea) and one or two species of Melania, more especially 

 M. cancellata of Cantor, likewise occur in the collection. A single 

 specimen of Meretrix {Cythei-ea, Lam.) zonaria (a rare shell), and 

 several others might be enumerated. 



7th. Another very interesting shell was brought by Dr. Lamprey, 

 a single specimen of a species of Unio, belonsing to a form which, 

 till very lately, had only been observed in North America. This 

 may be the Unio tientsinensis of Crosse and Debeaux ; but as it differs 

 in some respects from the figure given by these authors, we are in- 

 clined to consider it distinct. 



Unio (Lampsilis) subtortus, nob. (PI. XXVL figs. I, 1 a.) 



U. testa oblique ovata, valde incequilaterali, solida, venfricosa, 

 concentrice rugoso-striata, ad marginem dorsalem oblique no- 

 doso-pUcata ; valvis subtortis ; umbonibus lateralibus, promi- 

 nentibuSy erosis, ad apices tuberculosis ; margine dorsali con- 

 vexo ; margine ventrali ovato ; latere antico declivi, convexo ; 

 latere postico elongato, oblique ovato, obscure angulato ; epider- 

 mide olivaceo-fusca, sericea ; dentibus cardinalibus crassis, du- 

 plicibus, subverticalibus, sulcatis, dente valves sinistrce multum 

 majore ; dentibus lateralibus elongatis, subarcuatis, transverse 

 sulcatis, in valva sinistra duplicibus ; margarita albida. 

 Long. 55, alt. 50, lat. 28 mill. 

 Hab. Shanghai, North China (Dr. Lurnprey). 

 The nodose plications on the dorsal edge are elevated, but 

 worn. They appear almost to have been originally blunt spines. 

 The shell is longer than the species figured by Crosse, and not so 

 tumid. 



Unio (Dysnomia) lampreyanus, nob. (PI. XXVL figs. 2, 2a.) 



U. testa subtriangulari, incequilaterali, solida, conijiressa, concen- 

 trice late et valde plicata ; margine dorsali arcuato ; margiyie 

 ventrali arcuato ; latere antico circulari ; latere postico oblique 

 ovato; umbo7iibus prominentibus , erosis; epidermide nitida, 

 luteo-olivacea, fusco-viridi radiata ; dentibus cardinalibus 

 crassis, verticalibus, duplicibus, sulcatis ; dentibus lateralibus 



