xvi 



disk, to which (on account of its extreme tenuity) Dr. Carpenter 

 has designated 0. tenuissima. Both these types have recently 

 been made the subject of special monographs; the former by 

 Professor Loven,* who characterises it as " the most extraordi- 

 nary Echinoid hitherto known ; " and the latter by Dr. Car- 

 penter^ who finds in it the complete key to the pedigree of the 

 Orbitoline type, and makes it the basis of a Study in the Theory of 

 Descent. The total number of additions made by this expedition to 

 British shells (partly of species previously known, but new to British 

 seas, — partly of species previously known only as fossils, — and partly 

 of species altogether new to science) was so great, that Grwyn Jeffreys 

 spoke of them as requiring for their description an additional volume 

 of his Conchology. This, however, he never brought out ; but 

 communicated to the Zoological Society his descriptions of new 

 types. 



In the following year (1870) Grwyn Jeffreys again undertook the 

 charge of the earlier part of the " Porcupine" deep-sea explorations ; 

 which, it was arranged, should extend from Falmouth to the Straits 

 of Gibraltar, along the eastern border of the Atlantic basin. Although 

 his dredgings were not carried on at as great depths in this cruise as 

 they had been in the previous year, yet their results were not less 

 interesting. Thus, in one haul, at 994 fathoms off the coast of 

 Portugal, no fewer than 186 species of shells w T ere brought up, of which 

 71 were undescribed, whilst 24 were only known as fossil, less than 

 half having been previously described as existing species. In another 

 day's dredging in the same neighbourhood, at from 600 to 1095 

 fathoms' depth, several rare Siliceous Sponges and Echinoderms were 

 found ; but the great prize was a beautiful new species of Pentacrinus 

 — the first of that type ever met with in temperate seas — of which a 

 full account has recently been given by Dr. P. H. Carpenter,J under 

 the specific designation Wyville-Thomsoni, assigned to it by its dis- 

 coverer. 



The prevalence of northern forms in this deep-sea Fauna confirmed 

 Gwyn Jeffreys's previous views as to the southward extension of that 

 Fauna into the Mediterranean ; and perceiving the improbability that 

 in the existing condition of the Strait of Gibraltar any immigration 

 of bottom crawlers could take place, he threw out the suggestion in 



a similar generic type had been obtained in the previous year in the dredgings carried 

 on by Count Pourtales in the Grulf Stream, and had been named by Professor 

 Alexander Agassiz Pourtalesia miranda. As the " Porcupine " type proved specifi- 

 cally different, Professor W. Thomson designated it P. Jeffreysi. 



* " Kongl. Svenska Yetenskaps Anaderni ens Handlingar," 1883. 



f " Phil. Trans.," vol. 174, p. 551. 



X " Report on the Crinoidea collected during the Voyage of H.M.S. 1 Challenger,' " 

 Part I, pp. 313-321. 



