132 Biblioyraplticul Notices. 



eye, and is extremely difficult to be forced open against the will of the 

 animal. 



The fourth order, that of the Echinid^ or Sea-Urchins, is thus 

 introduced to our notice : — 



"Of equal importance to zoologist and geologist is the study of the Sea- 

 Urchins : to the former they present the perfection of radiism, as well as the 

 first steps towards a symmetrical or bilateral form ; to the latter the know- 

 ledge of their habits and organization is necessary in order to understand 

 the relations and associations of the numerous species wliich abound in many 

 of the earth's strata. Of all the Radiata they are most perfectly preserved 

 in a fossil state. Their hard calcareous integument, or shell, as it is popu- 

 larly but inaccurate])' termed, the parts of which are jointed together with 

 wondrous completeness, is especially durable ; consequently v/e find the hard 

 parts of the extinct species frequently as perfect as those of the recent ex- 

 amples preserved in our cabinets. 



"The Sea-Urchins are distinguished from all the other Echinoderms by 

 their form, which is more or less rounded, without arms of any kind, and by 

 their integument, in which calcareous matter is deposited so as to form se- 

 ries of regular plates, which plates are studded with tubercles, bearing 

 jointed on them spines of various forms and sizes according to the genus or 

 famil}'." 



" The EchinidcB progress by means of the joint action of their suckers and 

 spines, using the former in the manner of the Asteriadce, and the latter as 

 the Ophiundee do. Many Sea-Urchins, such as live on hard surfaces, 

 moor themselves also by means of the suckers, and thus adhere very 

 firmly to the rocks. That such is the mode of progression and rest among 

 this family I assert, not only from the general belief of naturalists, but also 

 from personal observation." 



On this point we can fully con-ohorate what the author has ad- 

 vanced, having repeatedly seen the common Urchin {Echinus sphcera) 

 moving about or anchoring at pleasure by means of its suckers. The 

 first time we noticed the fact was under circumstances which we still 

 very vividly remember. We had cut horizontally into two nearl}^ 

 equal parts a large Sea-Urchin, for the purpose of examining the in- 

 testine and ovaries. These being removed, the shell was thrown on 

 the deck of the little vessel, as being no longer of any service. It 

 chanced, however, that we afterwards picked up the parts and placed 

 them in a shallow vessel of sea- water. To our surprise, the suckers 

 were soon extended and the animal walked about apparently as un- 

 concerned as if the loss of intestine and ovaries had been an every- 

 day occurrence. 



Of the order Echinida there are seven genera and twelve species. 

 Brissus lyrifer is now for the first time described and figured, and 

 we have also for the first time figures of the E. Flemingii and lividus. 

 We have long been aware of the fact that the common Echinus of 

 the Mediterranean was a species distinct from our own, though both 

 had been included in the common appellation of E. esculentus. The 

 distinction is now announced by Mr. Forbes, and he gives the follow- 

 ing excellent characteristics for the family Echinida : — 



" The essential specific characters depend on the arrangement of the tu- 

 bercles which bear the spines, on the spines themselves, and on the number 

 and arrangement of the pairs of pores in the avenues of suckers. These pre- 



