REPORT ON THE CRUSTACEA MACRURA. 121 



Islands, at an average depth of 500 fathoms, on a muddy bottom, with a temperature 

 approximating to 39° "5. 



The genus Pentacheles appears to range as far as the limits of the great Pacific Ocean. 

 Species have been taken among the Australasian Islands, the Philippine and New Guinea 

 groups, near the middle of the ocean, about the Fiji and Kermadec groups, and along 

 the south coast of South America, from Juan Fernandez to Cape Horn. Most of 

 these w r ere taken in the open ocean some distance from land, and generally on a muddy 

 or oozy bottom formed of the debris of Globigerina and other Foraminifera. The depth 

 at which they were taken varied from 120 to 1375 fathoms, but generally it was about 

 500. Belonging to exceptionally shallow water was Stereomastis (Pentacheles) suhmi, a 

 species wdiich, together with Stereomastis (Pentacheles) auriculata, I have been induced 

 to separate from the other species and establish as an independent genus, in consecpuence 

 of their having no mastigobranchial plates attached to the podobranchise (see p. 14). 

 Stereomastis suhmi was captured within the narrow channels that separate the numerous 

 rocky islets from the coast of Western Patagonia. The species from exceptionally deep 

 water are Pentacheles obscura, a much damaged specimen taken north of New Guinea, 

 in 1070 fathoms, and Pentacheles hevis, obtained off Juan Fernandez, at a depth of 1375 

 fathoms, but this latter species is represented by a second specimen taken south of the 

 Philippine Islands, at a depth of only 500 fathoms. The temperature at the bottom 

 varied from 35°'5 to 41°'8, according to the greater or less depth of the ocean, and the 

 sea bottom, with one or two exceptions, is recorded as being formed either of mud or 

 Globigerina ooze. 



The general aspect of the animals, even when specifically distinct, bears a general 

 close resemblance, and the alteration of the branchial apparatus appears to have no im- 

 portant influence on the external appearance. In Pentacheles euthrix the mastigo- 

 branchial plates are of extreme tenuity, and reduced in size, while they are absent in 

 Stereomastis auriculata and Stereomastis suhmi. Yet the general character of their 

 habits appears to correspond. 



Willemozsia has been found in the middle of the North and South Atlantic Oceans. 

 It was also taken in the Pacific, about 500 miles from the coast of South America, at a 

 depth very nearly as great as that in the Atlantic, and at nearly similar temperatures, 

 namely, 34 0, 6 and 35°'5 at a depth of 1375 and 2225 fathoms, as compared with a 

 temperature of 36°'8 in the North, and 36° '4 in the South Atlantic Ocean, at 1900 fathoms. 

 As in the preceding genera, the sea bottom where they were taken consisted of Globigerin;i 

 ooze, a deposit sufficiently constant to induce us to believe that it is the common home of 

 all the species of the genera that make up this group. The exceptions to these are few. 

 only three, I believe, and these are in relation to Pentacheles euthrix and Polycheles 

 baccata, which were taken on a rocky and red clay bottom. 



Within certain limits it is therefore presumable that the family is represented by 



(ZOOL. CHALL. EXP. — PART HI. — 1886.) Fff 16 



