of the shell in a young larva, and which, as the larva grows, permeates 

 the whole animal until it is entirely yellow; (h) appearance of the shell 

 outline, which is relatively delicate when compared to the heavy outlines 

 of some other bivalve larvae with which Venus might otherwise be confused. 



OBSERVATIONS 



Wickford Harbor, 1950 



Weekly sampling in Wickford Harbor began April u, 1950 . On May 8, 

 sampling was intensified to a daily basis, as far as time permitted, at 

 three vertical levels, surface, mid-depth, and bottom. This schedule was 

 maintained until October 11, when weekly sampling was adopted again. 

 Sampling ceased October 23. The samples were taken in 6 to 10 feet of water 

 from a dock jutting out about 150 feet into the harbor. Surface tempera- 

 tures in Wickford Harbor during 1950 are shown in table 1 and figure 2. 



Mya larvae.— Quantitative estimates of Mya larval abundance derived 

 from these samplings are presented in figure 3 and table 2. Although an 

 occasional young Mya larva was seen during the previous week they did not 

 appear in quantity until the week of May 21, when the surface temperature 

 was about l!u0 e to lU.5° C. Peak abundance was reached during the week of 

 June 11 when the average of the highest daily counts of straight-hinge 

 larvae was close to 5,000 per 35 gallons of filtered sea water. Late umbone 

 stage larvae first appeared during the week of May 28 and reached a peak of 

 abundance the week of June 18 when about 300 per 35 gallons as a daily 

 average were counted. From mid-July to the first week in September no Mya 

 larvae were present in the samples. During the first 2 weeks of September 

 and again during the first 2 weeks of October there were larval concentra- 

 tions of up to 120 late umbone stage larvae per 35 gallons. 



Venus larvae.— Figure h and table 3 show the abundance of straight- 

 hinge and mature larvae during the 1950 spawning season by weekly averages. 

 Larvae appeared abruptly during the week of June 11 when the surface temper- 

 ature was about 18. 5* to 19° C„ This week showed the greatest abundance of 

 straight-hinge larvae of the summer, an average of a little over 3,000 per 

 35 gallons. Straight-hinge larvae were present each week, with two excep- 

 tions from June 11 until spawning ceased, about the second week of Septem- 

 ber. Late umbone stage larvae appeared during the week of June 18 and for 

 the next 3 weeks. The greatest abundance during this period was 300 per 

 35 gallons. Another group of late umbone stage larvae made its appearance 

 during the week of August 20. 



Wickford Harbor, 1951 



Samoling from the dock in Wickford Harbor began April 16, 1951, and 

 was continued without interruption through the spawning season, Both sur- 



