[2][3] For much of his career, his authority with respect to the classification of certain substantial groups of organisms was unchallenged: barnacles,[4][5] chitons,[6][7] North American terrestrial mollusks,[8][9][10][11] and others.

In 1887, he found employment in New York City as a proofreader, but soon met George Washington Tryon, the resident expert on mollusks at the Academy of Natural Sciences of Philadelphia, and architect and author of the ongoing multi-volume Manual of Concology.

He was, no doubt, impressed by the young man's talents as a proofreader, considerable expertise in technical illustration, and especially by his undeniable enthusiasm for the study of mollusks and substantial knowledge of the subject.

During the next five years he produced hundreds of detailed pages of the Manual of Conchology, preparing many of the plates himself, and founded The Nautilus, an influential journal of malacology which has survived into the 21st century.

It is notable that Pilsbry did not always confine himself to the several areas of study with which he was already closely associated, but rather would sometimes stray into other fields of science, from geology and paleontology to the taxonomy of brachiopods.

[16][17][18] His field work provided a steady supply of new specimens for study, dissection, and illustration, and a seemingly endless array of new species to name.

His intellectual reach extended even further, through joint efforts with other workers: especially notably Africa with Joseph Bequaert and the Japanese region with Yoichiro Hirase.