Pinnotheres.    From Wordnik.com.  [Facts and Arguments for Darwin] Reference

Squilla, and many Macrura, when adult usually reside under stones, in the clefts of rocks, holes in the earth, subterranean galleries, sand, etc., not to mention other deviations in habits such as are presented by the Hermit Crabs, Pinnotheres, etc., -- and secondly and especially because the peculiarities which distinguish the Zoea of this species particularly from other Zoeae (the employment of the anterior limbs for swimming, the furcate tail, the simple heart, the deficiency of the paired eyes and abdomen at first, etc.) are neither to be deduced from a retro-transfer of late-acquired advantages to this early period of life, nor to be regarded at all as advantages over other Zoeae which the larva might have acquired in the struggle for existence.    From Wordnik.com.  [Facts and Arguments for Darwin] Reference