NEW YORK — Sully Bonnelly and Richard Shaw have formed Sully Bonnelly Ltd. and will introduce a collection of special occasion dresses and eveningwear for early fall.

The company has opened a showroom and offices at 530 Seventh Ave. here. It will be represented in Dallas by Nat Ekelman and in Atlanta by Shapiro Sales. The line will be sold under the Sully Bonnelly label, with dresses wholesaling for $125 to $180, evening gowns for $210 to $230 and separates for $65 to $125. It is showing for the first time at this week’s market at the International Apparel Mart in Dallas.

Bonnelly, the designer, was most recently designer for The He-Ro Group’s Bill Blass Group, which closed last fall. He has also worked as an assistant designer for Oscar de la Renta and as a designer for the Julie Francis and Akira dress collections.

It was at Oscar de la Renta Ltd. that Richard Shaw and Bonnelly first met. Shaw, who is president of the company and oversees overall operations, had worked at de la Renta for the past 14 years, most recently as assistant to the president, Gerald Shaw, his father. Prior to that, he worked for the firm’s former Miss O division.

Shaw said the collection will be made by contractors here, except for knits, which will be produced in Hong Kong.

Shaw projects a volume of about $3 million for 1994, with an account base of large and small specialty stores.

“We feel this is a good time to go into business,” Shaw said.

He pointed out that the recent closings of several operations in the special occasion category, such as the Bill Blass Group, Oscar de la Renta Studio and Bob Mackie Boutique collections — all at The He-Ro Group, have created opportunities for new lines.