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Show 450 MR. ST. GEORGE MIVART ON THE [Julie 24, fusco-olivacea, concentrice plicato-striata, disco medio et postico rugis obliquis irregulariter angulatis, interdum granosis, hie prcesertim versus marginem ventralem obsoletis corrugato ; umbonibus non prominentibus, subplanulatis, angulatim corrugatis, haud procul ab extremitate anteriore positis; lunella parva, concava latere antico brevissimo subacuminato-rotundato; area convexa; margine dorsali postice regulariter convexo-curvato, terminaliter rotundato, ventrali convexo; dentibus cardinalibus crassis, radiatim corrugatis, in valva dextra binis, anteriore minimo, in sinistra ternis vel subternis; lateralibus elongatis subcurvatis, in valva dextra subduplicibus, in sinistra duplicibus; margarita colore salmonis tincta. Testa junior rotundato-ovalis, omnino preeter ad extremitatem anticam subradiatim granoso-plicifera. 1. 2. 3 (Testa junior). Long 52 45 34 Lat 35 32 26£ Crass 22 20 17 Ligamenti long 23 20^- 16 Hub. in flumine Iravadi ad Bhamo in regno Avae. I know of no Unio with which I can compare this. U. pellis lacerti, Mor., from Siam, is a little like it, but is much narrower and less inequivalve. Several other species of Unio occurring with U. burmanus appear to me to be rather varieties of named species than forms deserving a distinct name. In one or two cases I feel doubtful, however. All would unquestionably be described as new by many naturalists. It is worthy of note that some of them are more closely allied to forms occurring in the Brahmapooter river, in Assam, than to those inhabiting the lower Irawady valley, in Pegu. The land shells of Bhamo and its neighbourhood are mostly either identical with forms occurring in Cachar and Khasia, or closely allied to them; and it is a remarkable and interesting fact connected with freshwater shells to find that they coincide in their distribution with the land animals, and do not follow the lines of the rivers in which they live, thus adding another proof of the existence of a means of migration amongst them independent of the course of rivers. 7. Notes on the Myology of Menobranchus lateralis. By ST. G E O R G E M I V A R T , F.R.S., Lecturer on Comparative Anatomy at St. Mary's Hospital. The specimen which has served me for examination is one of those mentioned in m y paper on Menopoma as having been confided to m e from the stores of the Royal College of Surgeons. This well-known species with permanent external gills has a more slender form than Menopoma; it has also a narrower head and |
