HELIOMETRINAE 



141 



The specimens from Sts. 1 948-1 957, from the Bransfield Strait region, were fixed and 

 preserved by Mr J. W. S. Marr who made many notes concerning them. He writes, 

 from his observations on captured specimens, that the species is "very powerful and 

 active and swims with a remarkable grace of movement". Because of its activity it 

 breaks itself into pieces if killed in a confined space. The best results were obtained by 

 fixing in fresh water in ample space. 



The species has previously been taken from depths between 10 and 650 m.; the 

 majority of the present collection come from between 22 and 525 m. But eight speci- 

 mens were taken from 1080 m. in the Bransfield Strait (St. 177); they are all small but 

 they possess the usual twenty arms and do not appear abnormal. A pentacrinoid larva 

 was also taken at this station. 



Number of arms. The number of arms possessed by the specimens of this collection 

 are shown, under the localities from which they come, in the following table : 



The single abnormal specimen from South Georgia, with 22 arms, has eleven radials. 

 The twenty-one specimens with 16, 17, 18 and 19 arms from the Bransfield Strait all 

 come from one of the eight stations made in that region (St. 1952). Twenty-two speci- 

 mens with 20 arms were taken with them. They are much younger and smaller than 

 those with abnormal numbers of arms: their longest cirri consist of 25-38, mostly 30, 

 segments; those of most of the specimens with 16-19 arms are of 50-65 segments. 

 Five of the six specimens with abnormal numbers of arms from the Graham Land 

 region are of medium size, their longest cirri of 39-45 segments ; one is small, its longest 

 cirrus of 28 segments. 



In the 19-armed specimen from the Graham Land region (it is from St. 180) the 

 single arm arises from a normal radial which is followed by a regular ossicle slightly 

 longer than the costals of the other rays. Next is a still longer ossicle with a pinnule 

 arising from either side of it. It is succeeded by a syzygial pair with a pinnule arising from 

 the epizygal and beyond this the arm is normal. The single arms of the 19-armed and 

 17-armed specimens from the Bransfield Strait are different. The second ossicle beyond 

 the radial is shaped like an irregular axillary, and a pinnule arises from one side of it. It is 

 followed by a very short ossicle with no pinnules, which appears to correspond with the 

 first brachial of normal arms; after it comes a longer ossicle shaped like the second 

 brachial of normal arms, with a pinnule on the opposite side to the first. A syzygial pair 



