THE ENTOMOSTRACA OP LAKE BASSENTHWAITE. 125 



2 square miles in area. It is 3 - 83 miles in length, its average breadth 

 is "054 mile or 950 yards. The widest part of the lake is exactly f mile. 

 The surface of the Jake is 223"4 feet above the sea-level ; the average 

 depth is 18 feet : the greatest depth is 70 feet. Direct drainage-area 

 91tj square miles; total catchment-area 134 square miles. 



The upper end of the lake is shallow, and depths over 25 feet are 

 confined to a trough nearly 2 miles long in the middle of the lake. 

 The section across the lake suggests a double-troughed depression 

 separated by a broad central rise. Mill says : — " The steep slopes of 

 the lake above and below water were always composed of smooth 

 rounded stones, much smaller than the great blocks of Derwentwater ; 

 the stones were only observed to be covered with mud on the shallow 

 flats at the north-west and southern ends, and except for some rushes 

 and water-lilies in the south-eastern corner, thers were remarkably few 

 water-plants, and no signs of a peaty floor. Well out in the lake the 

 sediment was always found to be soft mud." The soundings were 

 taken on June 24th and 26th, 1893. 



On 4th April, 1897, a few tow-nettings were roughly made in the 

 lake, with the view of ascertaining the nature of the fauna. The follow- 

 ing forms were taken : — Copepoda : Cyclops strenuus, and C. signatus 

 were fairly common ; Cyclops affinis was rather rare. Daphnid^e : 

 Bosmina longirostris and the larvee of Leptodora hyalina were fairly 

 common. 



On 21st and 22nd April, and 15th, 16th, and 17th June, 1898, 

 the investigations were more thorough, and the middle and northern 

 portions of the lake were carefully worked at. 



In April ten tow-nettings were taken, six at the surface and four at 

 a depth of from 5 to 6 feet. The preservatives used were (1) a 

 solution of corrosive sublimate, and (2) a mixture of formol, spirit, and 

 osmic acid ; the latter obtained better results than the former. 



On 21st and 22nd April, 1898, it w r as noticed that the Copepods 

 were most abundant some little distance below the surface, while the 

 Daphnids were found in greatest numbers at the surface. The follow- 

 ing forms were taken : — Copepoda : Cyclops Kaufmanni L was very 

 abundant ; Cyclops signatus and Diaptomus gracilis w T ere abundant ; 

 Cyclops t7isignis, C. Ewarti, and C. strenuus, were less abundant ; 



1 This form is believed to be the young male of C. strenuus by Mr. Scour- 

 field, Nov. 20th, 1899. 



