Call:
lm(formula = ChelaLength ~ ShellSize, data = hcrabs)

Residuals:
     Min       1Q   Median       3Q      Max 
-1.53228 -0.09961 -0.01227  0.11390  0.63236 

Coefficients:
            Estimate Std. Error t value Pr(>|t|)    
(Intercept) -0.11437    0.05565  -2.055   0.0416 *  
ShellSize    0.29027    0.01435  20.232   <2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 

Residual standard error: 0.2339 on 146 degrees of freedom
Multiple R-squared: 0.7371,	Adjusted R-squared: 0.7353 
F-statistic: 409.3 on 1 and 146 DF,  p-value: < 2.2e-16

Chela Length = 0.29 * Shell Size - 0.11
R^2 = 0.7353
P < 2.2e-16