58 PROF. F. J. BELL ON THE [Feb. 19, 



These additions have, as may be supposed, led me to a careful 

 study of the generic and specific characters of these forms ; a work 

 in which, unfortunately, one has been able to gain but little assis- 

 tance from preceding naturalists. The only writer who stands in the 

 front rank of the students of Oreaster is Dr. Liitkeu ^ and of his 

 work, unhappily, I have been unable to make as full a use as I 

 should have done had he written in a language whose literature 

 was rich enough to justify the time necessary for learning it, or in 

 case I had understood a language which, when all is told, is not 

 spoken by a population exceeding one half that of this metropolis. 



I have, however, this satisfactory reflection, that in all, or nearly 

 all, the cases in which I have been able to understand him, there is 

 complete agreement between us. 



In the course of the paper I make use of some technical terms, 

 which are either new or have been but httle used ; and in so doing 

 I fear I shall bring on myself the wrath of Mr. Lyman for forcing 

 the reader to undergo a certain amount of " sawdust swallowing" " ; 

 but I shall, I believe, thereby adopt a method which is not only 

 approved by the philosopher and logician ^, and adopted by experts 

 in every branch of art and science, but one which will aid in the 

 two objects that ought now to be very dear to all zoologists — (a) the 

 condensation and assimilation of our technical descriptions, and ((3) 

 the preparation for a systematic method of formulation, by means of 

 which intellectual operations may be rendered more easy and more 

 rapid ^. 



It is convenient to have a single term for the line which divides 

 the dorsal surface of the arm into two halves ; where this line is most 

 apparent it has the form of a ridge, and I propose therefore to 

 speak of it as the lopJiial line, and of its spines as the lophial 

 spines. The five, often prominent, spines which are found at the 

 proximal end of the lophial lines may be called the apical spines, 

 while the term apical region may be well applied to the area con- 

 tained by the lines which join them to one another. 



I have seen no reason for departing from the use of the definite 

 terms siqieromaryinal and inferomarginal for the upper and lower 

 series of marginal plates ; nor can I propose any ciiange in the 

 terms for the adambulacral spinulation (monacanthid, diplacanthid, 

 and triplacanthid) which I suggested in the first of these " Contri- 

 butions'." 



Before commencing a systematic study of the species of this 

 genus it is necessary to make oneself acquainted with the character 

 of the modifications which the species undergo during growth. 

 Not only is it necessary to do this for the purpose of correctly 

 discriminating specific forms, but it would appear to be the mode 



1 Videnskabelige Meddelelser (Copenhagen), 1859, 18G4, 1871. 



2 See his lutroduction to his Eeport on the Ophiurids of the ' Challenger.' 



3 See Mill, Logic, 4th ed. ii. pp. 245-6. 



* Cf. Oweu, Phil. Trans. IBoLt, pp. 496-497 ; and AUuian, Eep. Brit. Assoc. 

 1863, p. 352. 

 ° P. Z. S. 1881, p. 499. 



