INVERTEBRATA, CEYPTOGAMIA, MICROSCOPY, ETC. 889 



Echini of the ' Challenger.'* — Professor Alexander Agassiz Las 

 just published a preliminary report on the Echini of the exploring 

 expedition of H.M.S. ' Challenger.' It was not Agassiz's intention to 

 publish this preliminary notice, as he hoped to be able to issue the 

 descriptions of the species with his final report on the group ; he 

 found himself, however, compelled, for the sake of retaining for the 

 material of the ' Challenger ' expedition the priority of discovery, to 

 notice, however briefly, the magnificent collection entrusted to his care 

 by Sir Wyville Thomson. 



In contrasting this collection with those made during the two 

 expeditions of the U.S. steamer ' Blake,' Agassiz says that these latter 

 contain some of the most interesting forms obtained by the former, 

 often complementing more or less imperfect ' Challenger ' material. 

 Among the Cidaridse, Arbteciadae, and Diadematidae many new species 

 were found, and a new genus allied to Astropyga. Among the Echino- 

 thurije, a number of new species were dredged. Of the Echino- 

 metradBB nothing of importance was collected. Among the Temno- 

 pleui-idas excellent series of the species of Salmacis and Temnopleurus 

 were obtained, a Cottaldia, hitherto only known from the chalk, and 

 an exquisite genus Prionechinus, allied to Salmacis. The most 

 interesting feature of the Echinidas proper was the occurrence of 

 several northern forms in deep water in the tropics. Not a single new 

 species of Clypeastroids was found, and the number of specimens even 

 was quite small. They do not play any important part in shaping the 

 character of the fauna of deep water, and are, perhaps, the most 

 strictly littoral group of Echini, indicative, at least in the present 

 epoch, of comparatively shallow water, inside of the 100-fathom line, 

 and probably giving us a good guide as to the depth of the sea and 

 the natiu'e of the bottom of the cretaceous and tertiary shores, where 

 they occur in such large numbers. One recent species of Catopygus is 

 interesting, as adding another of the cretaceous forms to those still 

 living. 



By far the most interesting group of Echini is that of the 

 Pourtalesice — the species were found in abundance ; of Pourtalesia 

 there are six species. In Cystechinus there are three species, 

 C Wyvillii and C. clypeatus have quite stout tests, while in 0. vesica 

 the test is reduced to a mere film, so that even in alcohol the shape of 

 this sea-urchin reminds one of the crown of an old felt hat which has 

 seen its best days. The test of all the Pourtalesice is quite delicate, 

 the amount of limestone being, at the great depths where they occiu', 

 reduced to a minimum, and yet even at the greatest dejiths they are 

 found associated with Ophiurans, which are by no means wanting in 

 lime. Among the Euspatangia, Spatangus p)urpureus occurred in the 

 tropics at a depth of 400 fathoms, and Echinocardium australe was 

 dredged at the great depth of 2675 fathoms. In Australia it is a 

 littoral zone species. Among the Brissina two species of Hemiaster 

 were obtained allied to S. prunella, a new species of Khinobrissus, and 

 two new ones of Schizaster. 



* 'Proc. Am. Acad. Arts aud Sci./ xiv. (1879) p. 190 ; 'Nature,' xx. (1879) 

 p. 53i. 



