The gastric mill on the genus Cyrtograpsus (Varunidae) has not been described previously. A morphological comparative study of the gastric mill ossicles within its species (C. angulatus, C. altimanus and C. affinis) was carried out. This research attempts to give new evidence to validate the existence of these three species and to serve as a guide to identify them. Urocardiac (dorsal median tooth shape), zygocardiac (shape and number of ridges and molar processes—cusps and plates—and their arrangement in the lateral teeth) and pectineal (number and shape of accessory teeth) ossicles, and cardiopyloric valve descriptions and comparisons are based on microscopical, stereomicroscopical, scanning electron microscope observations, and digital images. Morphological differences found in zygocardiac (lateral teeth) and urocardiac (dorsal-median tooth) ossicles allow to identify species. Considering these ossicles morphology in C. altimanus and C. affinis it can be concluded that the studied specimens belong to a single species as stated in morphometric and molecular comparative studies of the above species. These new data validate the existence of only two species (C. affinis and C. angulatus). This information will also be useful to recognize the species in the stomach content of their predators throughout the ossicles morphology.

The middle ear structures of nine species of golden moles (family Chrysochloridae) were examined under the light microscope. Auditory structures of several of these species are described here for the first time in detail, the emphasis being on the ossicular apparatus. Confirming previous observations, some golden moles (e.g. Amblysomus species) have ossicles of a morphology typical of mammals, whereas others (Chrysospalax, Chrysochloris, Cryptochloris and Eremitalpa species) have enormously hypertrophied mallei. Golden moles differ in the nature and extent of the interbullar connection, the shape of the tympanic membrane and that of the manubrium. The stapes has an unusual orientation, projecting dorsomedially from the incus. It has been proposed that hypertrophied ossicles in golden moles are adapted towards the detection of seismic vibrations. The functional morphology of the middle ear apparatus is reconsidered in this light, and it is proposed that adaptations towards low-frequency airborne hearing might have predisposed golden moles towards the evolution of seismic sensitivity through inertial bone conduction. The morphology of the middle ear apparatus sheds little light on the disputed ordinal position of the Chrysochloridae.