XC THE VOYAGE OF H.M.S. CHALLENGER. 



habit of our common Shrimp, for which purpose the ophthalmopods have become pro- 

 tected by the frontal margin of the carapace. 



They are mostly inhabitants of the warmer seas, abounding in tropical and subtropical 

 regions, becoming scarce in the temperate, and gradually disappearing towards the 

 subarctic regions. One specimen alone of Betseus truncatus is recorded by Dana from 

 Cape Horn, where it was dredged in 1 fathoms of water, with which exception none of 

 the family has been observed further south than New Zealand (50° S. lat.), or further 

 north than the English Channel (52° N. lat.). 



It is essentially a sublittoral form, for the instances of its being found beyond 20 

 fathoms are few, and these are suggestive of doubt, inasmuch as Alpheus avarus is 

 recorded in our collection as being taken off Tongatabu at a depth of 18 fathoms, and in 

 Mid-Pacific at 2675 fathoms, south of Japan. 



I am not aware that any species of this or the allied genera has been found fossil. 



The family of the Pasiphseidse is but poorly represented in the Challenger collection, 

 there being only three genera, Pasiphsea, Orphania, which are deep-sea forms, and 

 Leptochela, which, if found at the bottom, lives within 50 fathoms of the surface. It is 

 interesting to compare these species with a fossil form that has been much discussed 

 among geologists, but it appears to me that if the interpretation of Pygocephalus huxleyi 

 of Woodward 1 be correct, there can be little doubt that it is closely allied to the genus 

 Pasiphsea, and that it differs from Pasiphsea cristata (PL CXLI. fig. 1) in little that 

 cannot be considered as of merely specific importance. 



1 Trans. Geol. Soc. Glasgow, vol. ii. fig. 2, p. 243.. 



