For arbitrary m, n ∈ Z with gcd(2m, 3n) = 1 we denote by D = 4m 3 − 27n 2 = −3, −4 the discriminants which are squarefree, and we define the family of elliptic curves E D : y 2 = x 3 + 16D. These curves admit a rational 3-isogeny λ. In this paper we show that the rank of the λ-Selmer group of E D and of the λ-isogenous curves E D ′ = E −27D have specific values related to the 3-rank r 3 (D) of the ideal class group of the quadratic field. Employing a known result on the parity of X[E D ], we obtain that the rank of these curves is bounded below by 1 for D > 0 and by 2 for D < −4. Finally, we give an explicit, infinite subfamily of curves E D with D = −p, where p are primes of a specific form.