Fig. 4. Scatter plot showing _max values for MWS and LWS outer segments of individual double cones measured in coho salmon (Oncorhynchus kisutch, Walbaum). Vertical dotted lines predict the range of _max values for the MWS cones at the short wavelength range of the data set. Taking the lower value of 490₁ nm as the A₁ observed value, we used the Whitmore and Bowmaker model (Whitmore and Bowmaker, 1989) to calculate that the same opsin would have a _max of 516₂ nm if combined with an A₂ chromophore. Vertical dashed lines indicate the range for the longer of the two opsins, with a pigment pair that would have a range of 512₁ to 548₂ nm. The horizontal dotted lines predict the range for the shorter of the two proposed LWS cone opsins, having a pigment pair that extends from 545₁ to 600₂ nm based on Harosi's model (Harosi, 1994). Likewise, the horizontal dashed lines indicate the range for the longer of the two proposed LWS opsins, with a pigment pair that has a range of 563₁ to 633₂ nm. All data points fit between these vertical and horizontal limits within the measurement error of the MSP device (±3 nm), except those in the lower range of the LWS data set (see text).