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084 " THETIS " SCIENTIFIC KESULTS. 



upon close study that the muscles have been reduced from three 

 distinct original types, while the abbreviated arm tips occur in 

 one of the genera of the Thalassometridse. I have therefore 

 retained the family Tropiometridaj as covering TropioTnetra only, 

 a curious genus with no very close aHinities, created a new 

 family Calometridse containing four new genera for the numerous 

 species which I formerly placed in Calometra, and placed Ptilo- 

 metra, Fterornetra, and Asterometra in the Thalassometridse where 

 the}' undoubtedly belong. The Charitometridse I have made a 

 family instead of a subfamily, of equal rank with the family 

 Thalassometridse (formerly the subfamily Thalassometrinse). 



Recent discoveries have shown that the Zygometridse are not 

 nearly so sharply differentiated from the so-called Himorome- 

 tridse as was previously supposed, and it has seemed best to 

 •discard the latter family altogether, raising the three subfamilies 

 previously included within it to family rank. 



Explanation of Terms. 

 In the description of a Comatulid the number of the cirri is 

 ■expressed by Roman numerals, and the number of their com- 

 ponent segments by Arabic ; thus " cirri XVII, 25 " means that 

 the animal has seventeen cirri, each with twenty-five segments. 



'I'he division series are indicated by the lettei's " Br " preceded 

 by the number of the series, expressed in Roman numerals ; 

 thus "IBr" signifies the first division series following the radials, 

 the "costals" of P. H. Carpenter's terminology in his later 

 works, and the *' second and third radials " of the " Challenger " 

 Reports; "IIBr" is equivalent to "distichal series," "IIlBr" to 

 ^'palmar series," "IVBr" to "post-palmar series," etc. The 

 individual elements of the division series are indicated by so-called 

 inferior numbers ; thus IIBr2 means the " second distichal " or 

 tlie second ossicle of the second division series. 



The presence of a syzygy is indicated by the use of the symbol 

 •"-t-"; thus " IIBr4(3-f 4)" means that the second division series 

 is composed of four ossicles, of which the third and fourth are 

 ■united by syzygy. 



The outer pinnules of an arm are numbered in regular sequence, 

 Pj^, Pg, P3, etc. ; the inner pinnules are lettered Pa, P6, Pc, etc. 

 Tne IBr or " costal pinnule " (only found in the genus Eudiocri- 

 nus) is distinguished as Pc, the IIBr or " distichal pinnule " as 

 Pd, the IlIBr or "palmar pinnule" as Pp, the use of these 

 inferior capitals serving to differentiate these pinnules from those 

 ■of the inner side of the arm. 



