Some Aspects of the Cranial Morphology of Rana grayi Smith

Abstract

Summary.Only the points in which the cranial morphology of Rana grayi differs from that of the common European species of Rana will be given here. The anterior process of the crista subnasalis is comparatively long and projects forwards beyond the superior prenasal cartilage. A ventromedian process of the crista subnasalis appears in the palate, in this way separating the partes palatinæ of the premaxilla and the maxilla from each other. In the one specimen both the foramina frontalia are absent; in the other the normal condition obtains. The plica obliqua, which is poorly developed, is suspended from the cartilago obliqua and not from the tectum nasi. The posterior niche‐like portion of the vestibulum is practically absent. The two Gauppian “Wülste” are both present, but they are not demarcated sharply from each other. The recessus alaris and the infundibulum are smaller than in the European Rana. The cavum principale has a small ventromedian recess. An infundibular vestige of the recessus sacciformis is present. The musculus lateralis narium is slightly different from that of the European Rana. A small prechoanal pouch is present. The septomaxillary consists of an anterior unpaired portion which has three posteriorly directed processes. The nasals are much smaller than in the common European species of Rana. A peculiar cartilaginous plate, which is connected synchondrotically to the solum nasi, occurs on the ventral surface of the os en ceinture. A little further backwards a small cartilaginous cyst appears on either side of the os en ceinture. Both the parasphenoid and the fronto‐parietals are indented anteriorly. The exoccipital and the prootic do not fuse with each other. Rana grayi possesses a so‐called “Mundwinkeldrüse” situated between the palatal and the facial portions of the maxilla. The gland consists of adenoid tissue and has a lumen which opens into the buccal cavity. The pterygoid fuses with the processus oticus and with the processus basalis. In the one specimen the quadratomaxillary acquires a bony connection with the paraquadrate. A delicate rod‐like cartilage, which is connected synchondrotically to the symphysial cartilage, occurs on the ventral surface of the pars mentalis of the dentary.