LV.—A new trilobite,Acidaspis (Pseudomonaspis) magnospina,from the Coniston limestone

Summary

The morphology of adults and young of Acanthomia tomentosicollis Stål. and A. horrida, Germ. is described. Measurements of head-width and antennal segments of nymphs and adults were made. The heads of adults and nymphs of A. tomentosicollis are wider than those of A. horrida. The comparisons of head and antennal growth showed that the two species developed at about the same rate. Some of the morphological features of these species are remarkably primitive and are probably new features known in the Pentatomamorpha.