6 



EAST COAST MARINE SHELLS 



rich field. These have been burled for mil- 

 lions of years yet often show considerable 

 color and lustre. Many of the species were 

 the progenitors of those living In Florida 

 today. The opportunity for acquiring this 

 material Is without parallel and specimens 

 doubtless will be available upon the dikes 

 for several years to come. For additional 

 information pertaining to these shells the 

 reader should refer to Ball's monumental 

 work on the Tertiary Mollusca of Florida 

 which was published by the Wagner Free In- 

 stitute of Philadelphia and is still for 

 sale by that Institution. 



The Dredge 



In Woodward's Manual of the Mollus- 

 ca a practical small dredge is described 

 and illustrated. It is built of wrought 

 iron with movable Joints which permit fold- 

 ing and it may be carried in the hand. It 

 consists of two long narrow parallel pieces 

 each with a cutting edge. On the insldes 

 these are provided with eyeholes for the 

 attachment of a net and fastened with cop- 

 per wire. At the ends are fastened two 

 pieces of rawhide and at their extremities 

 a pair of rings. The towing rope in turn 

 Is attached to the rings. The ends and bot- 

 tom of the rawhide are connected by the net 

 made of cod-line which permits the water to 

 escape. The opening between the blades is 

 kept narrow to prevent the entrance of 

 large objects. There are various varia- 

 tions of this dredge which give good re- 

 sults. 



Fig. 3 

 Bucket dredge 



The bucket type dredge was designed 

 and very successfully used by Dr. Hedley of 

 the Australian Museum, Fig. 3. It is fool- 



proof and according to its designer never 

 falls to deliver a load from the bottom. 

 It may be used in the forty-pound size at a 

 depth of 500 feet or more. It consists of 

 a cone-shaped piece of rolled steel with 

 reinforced sides to which are attached the 

 ropes. There is no opening at the bottom. 

 Fitted in the top is a flange with 3/4" 

 bolts. After bringing up a load the flange 

 is removed and the contents removed with a 

 trowel and sifted through trays which have 

 been fitted with screen wire of various 

 sizes. An important adjunct to any dredge 

 is a strong swivel which should be placed 

 where the ropes meet. This prevents the 

 rope from spinning about while being brought 

 up and consequent loss of the dredge. The 

 flange is essential to holding the material 

 inside which otherwise would be affected by 

 swirling eddies during its transit to the 

 surface. With a calm sea it is not diffi- 

 cult to empty the bucket dredge when swung 

 from a davit and controlled from the dingy. 

 In rough water the bucket operates equally 

 well but must be emptied on the deck. The 

 author's first bucket dredge weighed forty 

 pounds and required two men to operate on 

 his boat the "Dusty." Upon a cruise to the 

 Gulf of Mexico he also carried a twenty- 

 pound bucket which operated equally well in 

 comparatively shallow water. Still smaller 

 sizes were experimented with and found too 

 light in weight. The small light dredge 

 first described is more suitable for ordi- 

 nary use. 



In operating any type of dredge the 

 length of towline required is usually dou- 

 ble the depth of the water. If too short 

 nothing will be obtained; if too long it 

 will be in danger of getting fast. On 

 rocky or unknown bottoms a safety device is 

 advised in order to prevent loss. A float 

 consisting of a life preserver or small wa- 

 ter-tight keg may be fastened by a light 

 line to the dredge and towed in rear. In 

 the event that the main rope breaks the 

 dredge may readily be recovered. 



A very simple and inexpensive dredge 

 consists of a piece of ordinary iron sewer 

 pipe, roughly 3 feet long and about 9 Inches 

 in diameter. One end is fitted with a re- 

 movable wooden plug, the other end bored 

 with 2 to 3 widely-spaced holes for attach- 

 ing the ropes. Several of these dredges 

 may be carried in a comparatively small 

 space and if lost are easily replaced. 



The various types of diving helmets, 



