The real Jenny Lind, as with all other melons, may have variable size depending on the growing conditions.

Here's a description from an SSE member who also got seeds of it from Pinetree:

75 days, green flesh melon with a small turban on the end, 2-4 #, sweet mild flavor.

Other SSE members say turban on the end and I think that's what you mean by knob, and size about 2#.

One member has a separate listing for one with no turban.

Skin should be netted, not ribbed.

When I grew it it was netted, had a distinct turban, and various fruits ranged between 1-2#.

I didn't think the taste was anything special. I think this variety became well known simply b/c it was rediscovered.

This has not been that great of a melon year in the NE, so I'm not that surprised with the small size of your fruits.

Weather can also influence fruit genetic traits.

Carolyn

Last year I tried growing Jenny Lind, and got a melon with netting, no ribbing and no turban. Decided I had incorrect seeds and requested more. So I tried again this year. This year's melons were netted and ribbed, but again no turban. The fruits have been about grapefruit sized. They turn a yellow/golden color when ripe and slip from the vine. They have been about as good as any of the melons I've grown this year, being as how it's been a cool, wet summer here. None have been extremely sweet. I'm still not 100% sure I've grown a true Jenny Lind though.