« …Therefore, it seems acceptable to consider Praehyalocylis ancestral to Hyalocylis. Considering the various fossil occurrences, the transition between these two genera must have taken place during the early to middle Miocene. As genetical differences between Hyalocylis and the Creseidae are also considerable, […] a family Hyalocylidae fam. nov. is here introduced to contain these two groups of species. » – A. W. janssen: “Notes on the systematics, morphology and biostratigraphy of holoplanktic Mollusca, 27”, Basteria vol. 84(1-3) p.70.
 

« Larval shell thimble-shaped, smooth, almost straight, obsolete. Adult shell transversely fluted, terminating posteriorly by a transversal septum surrounded by the chipped edges of the larval shell; slightly curved, the curvature ventrally convex; circular transversely. Mantle without appendices. » – H. Fol: Études sur le développement des mollusques. Premier mémoire: sur le développement des Ptéropodes, Paris 1875, p.177.